12 Ways to Reduce Water Consumption

A good cleaning process can minimize costs and add value to your product. With a bit of observation and planning, a well-designed industrial or critical cleaning process can reduce water consumption as well.
The most compelling reason to minimize water usage in cleaning is to control the cleaning and manufacturing process. Effective water management yields immediate benefits, including decreased operational costs; longer process bath life; better process control, including the washing, rinsing, and drying steps; lower waste stream management costs; and improved product quality.
1. PrecleanTo save water during final cleaning, pay attention to the initial processes. Soil that has been left on the part is very adherent. Time and again, we observe the benefits of precleaning—notably, a shortened final cleaning cycle.
Precleaning also tends to decrease overall manufacturing time and rework as well as decreasing water usage. Make the initial cleaning convenient and effective, or your assemblers will simply ignore the precleaning step and pass the problem forward.
2. Choose the Right Cleaning AgentSelect the correct cleaning agent for your application, and coordinate that selection with the right cleaning system. Selecting a “default” cleaning agent and choosing a cleaning system out of a catalog is often not the most cost-effective way to go. Many critical cleaning processes have a very narrow window. If you are even a little off the mark in choosing the cleaning agent, you will end up wasting far more water than you ought to.
Understand the mix of soils, the materials of construction, the product configuration, and the expected end use of the product. Soils may be dissolved or suspended, or they may react with the cleaning agent. Soils may be organic, or they may be inorganic salts or metals. Even water-soluble or synthetic lubricants typically contain organic compounds. Some soils are particulate; the size and nature of the particles may determine the strategy for removal.
Select a cleaning agent that can be regenerated using oil separation and filtration, and that has a high soil loading for the soils of interest. It is often instructive to do pilot testing, because soil loading studies do not necessarily indicate actual cleaning efficiency.
3. Choose the Right Cleaning SystemIn-line, spray-in-air systems are often considered the only efficient design for high-volume cleaning. However, spray-in-air is inherently a line-of-sight process. For complex parts, spray pattern, force and direction must be fastidiously controlled; if not, cleaning will be inefficient and ineffective. Ineffective cleaning often necessitates re-cleaning. This means lost water, lost time, and higher process costs, not to mention lower product quality.
Consider batch systems with the option for turbulation, spray under immersion, and ultrasonics. For very complex workpieces, selecting an effective cleaning force means more rapid cleaning, sometimes at lower temperature.
In comparing cleaning systems, consider the impact of evaporation. Spraying the cleaning and/or rinsing agent produces a high surface area that, along with heating, contributes to evaporation. Where spray-in-air is used, the cleaning system should be designed to minimize losses through evaporation.
4. Optimize Cleaning StepsThe basic cleaning process consists of washing, rinsing, and drying. In the wash step, selecting a sub-optimal cleaning agent or failing to control the washing bath effectively wastes water directly and indirectly. One example of a direct effect is shortened bath life; every time you change the bath, you lose significant amounts of water.
An indirect effect is excessive water needed in longer rinse steps, either to remove cleaning agent residue or to achieve better removal of lubricants and related process materials in the rinse step rather than the wash step. Lack of attention to drying means recontamination of the part and spotting, often resulting in the need to reclean; with each cleaning cycle, some water is used.
5. Recover Wash and Rinse ChemistriesGenerally, oil-splitting chemistries are used in industrial cleaning agents. Oil can be skimmed off the top of the cleaning solution, minimizing soil loading and extending cleaning agent life. With dip or immersion tanks, this means that oil must be constantly removed from the top with a sparger or weir to avoid recontaminating the product when it is removed from the tank. With in-line spray systems, oil removal from the cleaning agent tank is a separate operation.6. Use Closed-loop RinsingA true “closed-loop” cleaning system is probably unachievable, sort of like the goal of zero residue. However, many options are available that allow effective cleaning and decrease water use. Reverse-cascade, where the final rinse is the cleanest water, is an effective means of decreasing water usage.
Some batch systems use a Quick Dump Rinse (QDR). In QDR systems, the parts stay in one tank; cleaning agent(s) and rinse agents are then added sequentially. Spray is typically used to avoid soil redeposition. Successive small rinses used in QDR can provide more effective soil removal with less water usage than a single rinse with a higher volume of water.
7. Use Consistent, Well-Defined WaterWater is a process chemical. As such, it has an inherent value. Defining water quality and achieving consistent water properties results in a more consistent process. This does not necessarily mean you have to use 18-MΩ water. High-resistivity water tends to erode the surfaces of metals because the water is “hungry” for ions.
To avoid “ion-hungry water,” and perhaps to decrease costs, some cleaning agent suppliers suggest using city water for certain applications. We disagree. In our experience, city water creates problems because it has inconsistent properties. We have seen too many process failures—with associated rework, recleaning and excessive water usage—where the culprit is use of city water.
Avoiding city water is particularly important in areas of poor water quality, in locations where water quality varies with the season, and in locations where requirements to manage the waste stream are, shall we say, spotty.8. Use Effective FiltrationProper filtration saves water and improves process performance and consistency. It may be used in preparation of the cleaning agent, to limit soil buildup during the process, to prepare water for the wash and rinse cycle, to regenerate rinse water in closed-loop systems and to meet requirements for waste stream quality.
Choosing the right filtration system should be a collaborative effort so that filtration can be meshed with the cleaning process. There are several steps:
1) Are the contaminants particulate or dissolved? 2) If particulate, what is their size and shape? 3) Are they organic? 4) Is there only one type of contaminant or are there many?
Filter selection is process-specific. Remember that filters are designed to trap spheres; contaminants are rarely cooperative in their shape, and most are not spherical. In addition, use of emulsifying oils can complicate the choice of filtration system. Such lubricants form stable emulsions. They can be removed, but at the cost of also removing cleaning agents. Once it’s installed, protect the filter. If filtering very small particles, consider a pre-filter or polishing filter. This is a coarser, somewhat sacrificial filter placed upstream to trap larger particles.
9. Monitor and Maintain Wash and Rinse FluidsAvoid extremes in bath monitoring and maintenance. At one extreme, people discard baths after a single use, a practice that may have a limited appeal in small, high-end applications, but is rarely practical and uses excessive amounts of water. At the other extreme, certain brave souls proclaim not having changed the wash tank for upwards of two years. Such tanks often resemble an aquarium or polluted river. Such folks may sporadically add cleaning agent and water, with little to no understanding of bath attributes.
It is more prudent to avoid either extreme and to set up change-out schedules. Such schedules may be arbitrary or they may be based on experience—i.e., process failures. Certainly, a changeout schedule can be valuable in process control. In critical cleaning applications involving products such as medical devices, pharmaceuticals, aerospace components and microelectronics, a changeout schedule may be a prudent option.
A rotary group from hydraulic pump rebuild, before and after cleaning. Photos courtesy Western Hydrostatics, Inc.
Adding water and cleaning agent at a predetermined rate is usually preferable to and less disruptive than simply dumping the wash tank. Wash bath attributes can be tracked by titration to check pH, by refractive index or by conductivity. The technique of choice depends on the cleaning agent and soil(s). Systems are available to automatically monitor bath(s) and to adjust appropriately either with cleaning chemistry or with water. Automation of bath monitoring takes away the human variable and tends to result in a more consistent bath.
Consider microbial monitoring. Sterility is a given in the medical and pharmaceutical worlds, and controlling biological materials is important. Microbial monitoring is sometimes used for metalworking fluids and to monitor high-quality water. For all processes, consider that cleaning agents or rinsing agents, particularly at near-neutral pH and gently heated, can support microbial growth. Contaminated baths have to be disposed of and process equipment has to be cleaned. This wastes time, money, and, of course, uses great quantities of water.
Monitor wastewater as well as cleaning and rinse waters. Changes in waste water may point to issues with the cleaning system, and keeping track of them can increase bath life, save water and, of course, improve performance.
10. Provide Training and Schedule MaintenanceA regular maintenance program is a must. Clogged nozzles lead to ineffective cleaning; this leads to more rework and to higher water usage. The people who operate your cleaning systems need explicit instructions and, because many cleaning systems are complex, they need to understand why they are doing what they are doing.
Training must be ongoing, particularly where there are personnel changes. A new worker might arbitrarily discontinue a rinse step because he or she does not know how to operate the equipment. While it might seem that eliminating the rinse would save some water, the uncontrolled steps needed to achieve your required level of cleanliness can actually waste water.
11. Analyze and Customize Your ProcessesWould you use the same process to wash your baby as you would to wash your car? Of course not, but sometimes general, industrial cleaning and critical final cleaning are carried out in a single system. Customize the cleaning processes to your facility and to the mix of parts you’re cleaning. Analyzing substrates, soils and the degree of cleanliness required. One large, central system may not outperform several smaller systems. Also consider that one process may not clean everything. We often find that problem parts or assemblies are cleaned repeatedly, using small, dedicated runs in large pieces of equipment. Each process run uses water and also wastes time and labor. If possible, change the soil, or consider a smaller, dedicated cleaning system.
12. Manage the ProcessMany aspects of customizing the cleaning process to reduce water usage are common sense, and you understand your process requirements better than anyone. However, it’s also easy to lose perspective if you look at the process day in and day out. Consider having an independent (non-vendor) assessment of cleaning process management and effectiveness, minimizing water usage. If, despite your best efforts, your cleaning system uses enough water to supply a small town and if the parts are still not cleaned effectively and in a timely manner, you are probably wasting water and business resources. In such cases, investigate contained, responsible use of solvents.

source A good cleaning process can minimize costs and add value to your product. With a bit of observation and planning, a well-designed industrial or critical cleaning process can reduce water consumption as well.
The most compelling reason to minimize water usage in cleaning is to control the cleaning and manufacturing process. Effective water management yields immediate benefits, including decreased operational costs; longer process bath life; better process control, including the washing, rinsing, and drying steps; lower waste stream management costs; and improved product quality.
1. PrecleanTo save water during final cleaning, pay attention to the initial processes. Soil that has been left on the part is very adherent. Time and again, we observe the benefits of precleaning—notably, a shortened final cleaning cycle.
Precleaning also tends to decrease overall manufacturing time and rework as well as decreasing water usage. Make the initial cleaning convenient and effective, or your assemblers will simply ignore the precleaning step and pass the problem forward.
2. Choose the Right Cleaning AgentSelect the correct cleaning agent for your application, and coordinate that selection with the right cleaning system. Selecting a “default” cleaning agent and choosing a cleaning system out of a catalog is often not the most cost-effective way to go. Many critical cleaning processes have a very narrow window. If you are even a little off the mark in choosing the cleaning agent, you will end up wasting far more water than you ought to.
Understand the mix of soils, the materials of construction, the product configuration, and the expected end use of the product. Soils may be dissolved or suspended, or they may react with the cleaning agent. Soils may be organic, or they may be inorganic salts or metals. Even water-soluble or synthetic lubricants typically contain organic compounds. Some soils are particulate; the size and nature of the particles may determine the strategy for removal.
Select a cleaning agent that can be regenerated using oil separation and filtration, and that has a high soil loading for the soils of interest. It is often instructive to do pilot testing, because soil loading studies do not necessarily indicate actual cleaning efficiency.
3. Choose the Right Cleaning SystemIn-line, spray-in-air systems are often considered the only efficient design for high-volume cleaning. However, spray-in-air is inherently a line-of-sight process. For complex parts, spray pattern, force and direction must be fastidiously controlled; if not, cleaning will be inefficient and ineffective. Ineffective cleaning often necessitates re-cleaning. This means lost water, lost time, and higher process costs, not to mention lower product quality.
Consider batch systems with the option for turbulation, spray under immersion, and ultrasonics. For very complex workpieces, selecting an effective cleaning force means more rapid cleaning, sometimes at lower temperature.
In comparing cleaning systems, consider the impact of evaporation. Spraying the cleaning and/or rinsing agent produces a high surface area that, along with heating, contributes to evaporation. Where spray-in-air is used, the cleaning system should be designed to minimize losses through evaporation.
4. Optimize Cleaning StepsThe basic cleaning process consists of washing, rinsing, and drying. In the wash step, selecting a sub-optimal cleaning agent or failing to control the washing bath effectively wastes water directly and indirectly. One example of a direct effect is shortened bath life; every time you change the bath, you lose significant amounts of water.
An indirect effect is excessive water needed in longer rinse steps, either to remove cleaning agent residue or to achieve better removal of lubricants and related process materials in the rinse step rather than the wash step. Lack of attention to drying means recontamination of the part and spotting, often resulting in the need to reclean; with each cleaning cycle, some water is used.
5. Recover Wash and Rinse ChemistriesGenerally, oil-splitting chemistries are used in industrial cleaning agents. Oil can be skimmed off the top of the cleaning solution, minimizing soil loading and extending cleaning agent life. With dip or immersion tanks, this means that oil must be constantly removed from the top with a sparger or weir to avoid recontaminating the product when it is removed from the tank. With in-line spray systems, oil removal from the cleaning agent tank is a separate operation.6. Use Closed-loop RinsingA true “closed-loop” cleaning system is probably unachievable, sort of like the goal of zero residue. However, many options are available that allow effective cleaning and decrease water use. Reverse-cascade, where the final rinse is the cleanest water, is an effective means of decreasing water usage.
Some batch systems use a Quick Dump Rinse (QDR). In QDR systems, the parts stay in one tank; cleaning agent(s) and rinse agents are then added sequentially. Spray is typically used to avoid soil redeposition. Successive small rinses used in QDR can provide more effective soil removal with less water usage than a single rinse with a higher volume of water.
7. Use Consistent, Well-Defined WaterWater is a process chemical. As such, it has an inherent value. Defining water quality and achieving consistent water properties results in a more consistent process. This does not necessarily mean you have to use 18-MΩ water. High-resistivity water tends to erode the surfaces of metals because the water is “hungry” for ions.
To avoid “ion-hungry water,” and perhaps to decrease costs, some cleaning agent suppliers suggest using city water for certain applications. We disagree. In our experience, city water creates problems because it has inconsistent properties. We have seen too many process failures—with associated rework, recleaning and excessive water usage—where the culprit is use of city water.
Avoiding city water is particularly important in areas of poor water quality, in locations where water quality varies with the season, and in locations where requirements to manage the waste stream are, shall we say, spotty.8. Use Effective FiltrationProper filtration saves water and improves process performance and consistency. It may be used in preparation of the cleaning agent, to limit soil buildup during the process, to prepare water for the wash and rinse cycle, to regenerate rinse water in closed-loop systems and to meet requirements for waste stream quality.
Choosing the right filtration system should be a collaborative effort so that filtration can be meshed with the cleaning process. There are several steps:
1) Are the contaminants particulate or dissolved? 2) If particulate, what is their size and shape? 3) Are they organic? 4) Is there only one type of contaminant or are there many?
Filter selection is process-specific. Remember that filters are designed to trap spheres; contaminants are rarely cooperative in their shape, and most are not spherical. In addition, use of emulsifying oils can complicate the choice of filtration system. Such lubricants form stable emulsions. They can be removed, but at the cost of also removing cleaning agents. Once it’s installed, protect the filter. If filtering very small particles, consider a pre-filter or polishing filter. This is a coarser, somewhat sacrificial filter placed upstream to trap larger particles.
9. Monitor and Maintain Wash and Rinse FluidsAvoid extremes in bath monitoring and maintenance. At one extreme, people discard baths after a single use, a practice that may have a limited appeal in small, high-end applications, but is rarely practical and uses excessive amounts of water. At the other extreme, certain brave souls proclaim not having changed the wash tank for upwards of two years. Such tanks often resemble an aquarium or polluted river. Such folks may sporadically add cleaning agent and water, with little to no understanding of bath attributes.
It is more prudent to avoid either extreme and to set up change-out schedules. Such schedules may be arbitrary or they may be based on experience—i.e., process failures. Certainly, a changeout schedule can be valuable in process control. In critical cleaning applications involving products such as medical devices, pharmaceuticals, aerospace components and microelectronics, a changeout schedule may be a prudent option.
A rotary group from hydraulic pump rebuild, before and after cleaning. Photos courtesy Western Hydrostatics, Inc.
Adding water and cleaning agent at a predetermined rate is usually preferable to and less disruptive than simply dumping the wash tank. Wash bath attributes can be tracked by titration to check pH, by refractive index or by conductivity. The technique of choice depends on the cleaning agent and soil(s). Systems are available to automatically monitor bath(s) and to adjust appropriately either with cleaning chemistry or with water. Automation of bath monitoring takes away the human variable and tends to result in a more consistent bath.
Consider microbial monitoring. Sterility is a given in the medical and pharmaceutical worlds, and controlling biological materials is important. Microbial monitoring is sometimes used for metalworking fluids and to monitor high-quality water. For all processes, consider that cleaning agents or rinsing agents, particularly at near-neutral pH and gently heated, can support microbial growth. Contaminated baths have to be disposed of and process equipment has to be cleaned. This wastes time, money, and, of course, uses great quantities of water.
Monitor wastewater as well as cleaning and rinse waters. Changes in waste water may point to issues with the cleaning system, and keeping track of them can increase bath life, save water and, of course, improve performance.
10. Provide Training and Schedule MaintenanceA regular maintenance program is a must. Clogged nozzles lead to ineffective cleaning; this leads to more rework and to higher water usage. The people who operate your cleaning systems need explicit instructions and, because many cleaning systems are complex, they need to understand why they are doing what they are doing.
Training must be ongoing, particularly where there are personnel changes. A new worker might arbitrarily discontinue a rinse step because he or she does not know how to operate the equipment. While it might seem that eliminating the rinse would save some water, the uncontrolled steps needed to achieve your required level of cleanliness can actually waste water.
11. Analyze and Customize Your ProcessesWould you use the same process to wash your baby as you would to wash your car? Of course not, but sometimes general, industrial cleaning and critical final cleaning are carried out in a single system. Customize the cleaning processes to your facility and to the mix of parts you’re cleaning. Analyzing substrates, soils and the degree of cleanliness required. One large, central system may not outperform several smaller systems. Also consider that one process may not clean everything. We often find that problem parts or assemblies are cleaned repeatedly, using small, dedicated runs in large pieces of equipment. Each process run uses water and also wastes time and labor. If possible, change the soil, or consider a smaller, dedicated cleaning system.
12. Manage the ProcessMany aspects of customizing the cleaning process to reduce water usage are common sense, and you understand your process requirements better than anyone. However, it’s also easy to lose perspective if you look at the process day in and day out. Consider having an independent (non-vendor) assessment of cleaning process management and effectiveness, minimizing water usage. If, despite your best efforts, your cleaning system uses enough water to supply a small town and if the parts are still not cleaned effectively and in a timely manner, you are probably wasting water and business resources. In such cases, investigate contained, responsible use of solvents.

source A good cleaning process can minimize costs and add value to your product. With a bit of observation and planning, a well-designed industrial or critical cleaning process can reduce water consumption as well.
The most compelling reason to minimize water usage in cleaning is to control the cleaning and manufacturing process. Effective water management yields immediate benefits, including decreased operational costs; longer process bath life; better process control, including the washing, rinsing, and drying steps; lower waste stream management costs; and improved product quality.
1. PrecleanTo save water during final cleaning, pay attention to the initial processes. Soil that has been left on the part is very adherent. Time and again, we observe the benefits of precleaning—notably, a shortened final cleaning cycle.
Precleaning also tends to decrease overall manufacturing time and rework as well as decreasing water usage. Make the initial cleaning convenient and effective, or your assemblers will simply ignore the precleaning step and pass the problem forward.
2. Choose the Right Cleaning AgentSelect the correct cleaning agent for your application, and coordinate that selection with the right cleaning system. Selecting a “default” cleaning agent and choosing a cleaning system out of a catalog is often not the most cost-effective way to go. Many critical cleaning processes have a very narrow window. If you are even a little off the mark in choosing the cleaning agent, you will end up wasting far more water than you ought to.
Understand the mix of soils, the materials of construction, the product configuration, and the expected end use of the product. Soils may be dissolved or suspended, or they may react with the cleaning agent. Soils may be organic, or they may be inorganic salts or metals. Even water-soluble or synthetic lubricants typically contain organic compounds. Some soils are particulate; the size and nature of the particles may determine the strategy for removal.
Select a cleaning agent that can be regenerated using oil separation and filtration, and that has a high soil loading for the soils of interest. It is often instructive to do pilot testing, because soil loading studies do not necessarily indicate actual cleaning efficiency.
3. Choose the Right Cleaning SystemIn-line, spray-in-air systems are often considered the only efficient design for high-volume cleaning. However, spray-in-air is inherently a line-of-sight process. For complex parts, spray pattern, force and direction must be fastidiously controlled; if not, cleaning will be inefficient and ineffective. Ineffective cleaning often necessitates re-cleaning. This means lost water, lost time, and higher process costs, not to mention lower product quality.
Consider batch systems with the option for turbulation, spray under immersion, and ultrasonics. For very complex workpieces, selecting an effective cleaning force means more rapid cleaning, sometimes at lower temperature.
In comparing cleaning systems, consider the impact of evaporation. Spraying the cleaning and/or rinsing agent produces a high surface area that, along with heating, contributes to evaporation. Where spray-in-air is used, the cleaning system should be designed to minimize losses through evaporation.
4. Optimize Cleaning StepsThe basic cleaning process consists of washing, rinsing, and drying. In the wash step, selecting a sub-optimal cleaning agent or failing to control the washing bath effectively wastes water directly and indirectly. One example of a direct effect is shortened bath life; every time you change the bath, you lose significant amounts of water.
An indirect effect is excessive water needed in longer rinse steps, either to remove cleaning agent residue or to achieve better removal of lubricants and related process materials in the rinse step rather than the wash step. Lack of attention to drying means recontamination of the part and spotting, often resulting in the need to reclean; with each cleaning cycle, some water is used.
5. Recover Wash and Rinse ChemistriesGenerally, oil-splitting chemistries are used in industrial cleaning agents. Oil can be skimmed off the top of the cleaning solution, minimizing soil loading and extending cleaning agent life. With dip or immersion tanks, this means that oil must be constantly removed from the top with a sparger or weir to avoid recontaminating the product when it is removed from the tank. With in-line spray systems, oil removal from the cleaning agent tank is a separate operation.6. Use Closed-loop RinsingA true “closed-loop” cleaning system is probably unachievable, sort of like the goal of zero residue. However, many options are available that allow effective cleaning and decrease water use. Reverse-cascade, where the final rinse is the cleanest water, is an effective means of decreasing water usage.
Some batch systems use a Quick Dump Rinse (QDR). In QDR systems, the parts stay in one tank; cleaning agent(s) and rinse agents are then added sequentially. Spray is typically used to avoid soil redeposition. Successive small rinses used in QDR can provide more effective soil removal with less water usage than a single rinse with a higher volume of water.
7. Use Consistent, Well-Defined WaterWater is a process chemical. As such, it has an inherent value. Defining water quality and achieving consistent water properties results in a more consistent process. This does not necessarily mean you have to use 18-MΩ water. High-resistivity water tends to erode the surfaces of metals because the water is “hungry” for ions.
To avoid “ion-hungry water,” and perhaps to decrease costs, some cleaning agent suppliers suggest using city water for certain applications. We disagree. In our experience, city water creates problems because it has inconsistent properties. We have seen too many process failures—with associated rework, recleaning and excessive water usage—where the culprit is use of city water.
Avoiding city water is particularly important in areas of poor water quality, in locations where water quality varies with the season, and in locations where requirements to manage the waste stream are, shall we say, spotty.8. Use Effective FiltrationProper filtration saves water and improves process performance and consistency. It may be used in preparation of the cleaning agent, to limit soil buildup during the process, to prepare water for the wash and rinse cycle, to regenerate rinse water in closed-loop systems and to meet requirements for waste stream quality.
Choosing the right filtration system should be a collaborative effort so that filtration can be meshed with the cleaning process. There are several steps:
1) Are the contaminants particulate or dissolved? 2) If particulate, what is their size and shape? 3) Are they organic? 4) Is there only one type of contaminant or are there many?
Filter selection is process-specific. Remember that filters are designed to trap spheres; contaminants are rarely cooperative in their shape, and most are not spherical. In addition, use of emulsifying oils can complicate the choice of filtration system. Such lubricants form stable emulsions. They can be removed, but at the cost of also removing cleaning agents. Once it’s installed, protect the filter. If filtering very small particles, consider a pre-filter or polishing filter. This is a coarser, somewhat sacrificial filter placed upstream to trap larger particles.
9. Monitor and Maintain Wash and Rinse FluidsAvoid extremes in bath monitoring and maintenance. At one extreme, people discard baths after a single use, a practice that may have a limited appeal in small, high-end applications, but is rarely practical and uses excessive amounts of water. At the other extreme, certain brave souls proclaim not having changed the wash tank for upwards of two years. Such tanks often resemble an aquarium or polluted river. Such folks may sporadically add cleaning agent and water, with little to no understanding of bath attributes.
It is more prudent to avoid either extreme and to set up change-out schedules. Such schedules may be arbitrary or they may be based on experience—i.e., process failures. Certainly, a changeout schedule can be valuable in process control. In critical cleaning applications involving products such as medical devices, pharmaceuticals, aerospace components and microelectronics, a changeout schedule may be a prudent option.
A rotary group from hydraulic pump rebuild, before and after cleaning. Photos courtesy Western Hydrostatics, Inc.
Adding water and cleaning agent at a predetermined rate is usually preferable to and less disruptive than simply dumping the wash tank. Wash bath attributes can be tracked by titration to check pH, by refractive index or by conductivity. The technique of choice depends on the cleaning agent and soil(s). Systems are available to automatically monitor bath(s) and to adjust appropriately either with cleaning chemistry or with water. Automation of bath monitoring takes away the human variable and tends to result in a more consistent bath.
Consider microbial monitoring. Sterility is a given in the medical and pharmaceutical worlds, and controlling biological materials is important. Microbial monitoring is sometimes used for metalworking fluids and to monitor high-quality water. For all processes, consider that cleaning agents or rinsing agents, particularly at near-neutral pH and gently heated, can support microbial growth. Contaminated baths have to be disposed of and process equipment has to be cleaned. This wastes time, money, and, of course, uses great quantities of water.
Monitor wastewater as well as cleaning and rinse waters. Changes in waste water may point to issues with the cleaning system, and keeping track of them can increase bath life, save water and, of course, improve performance.
10. Provide Training and Schedule MaintenanceA regular maintenance program is a must. Clogged nozzles lead to ineffective cleaning; this leads to more rework and to higher water usage. The people who operate your cleaning systems need explicit instructions and, because many cleaning systems are complex, they need to understand why they are doing what they are doing.
Training must be ongoing, particularly where there are personnel changes. A new worker might arbitrarily discontinue a rinse step because he or she does not know how to operate the equipment. While it might seem that eliminating the rinse would save some water, the uncontrolled steps needed to achieve your required level of cleanliness can actually waste water.
11. Analyze and Customize Your ProcessesWould you use the same process to wash your baby as you would to wash your car? Of course not, but sometimes general, industrial cleaning and critical final cleaning are carried out in a single system. Customize the cleaning processes to your facility and to the mix of parts you’re cleaning. Analyzing substrates, soils and the degree of cleanliness required. One large, central system may not outperform several smaller systems. Also consider that one process may not clean everything. We often find that problem parts or assemblies are cleaned repeatedly, using small, dedicated runs in large pieces of equipment. Each process run uses water and also wastes time and labor. If possible, change the soil, or consider a smaller, dedicated cleaning system.
12. Manage the ProcessMany aspects of customizing the cleaning process to reduce water usage are common sense, and you understand your process requirements better than anyone. However, it’s also easy to lose perspective if you look at the process day in and day out. Consider having an independent (non-vendor) assessment of cleaning process management and effectiveness, minimizing water usage. If, despite your best efforts, your cleaning system uses enough water to supply a small town and if the parts are still not cleaned effectively and in a timely manner, you are probably wasting water and business resources. In such cases, investigate contained, responsible use of solvents.

source .pfonline.com/articles/030903.html

Electroplating/Electroless Plating for Electronic Applications

Plating, including electroplating and electroless plating of metals and alloys, serves many useful functions in electronic devices: corrosion protection, diffusion barriers, conductive circuit elements, via-hole filling for semiconductor integrated circuits, through-hole connections for printed wiring boards and flexible circuits. Plating is used to fabricate passive devices on dielectric surfaces such as resistors, capacitors, inductors and to improve conductivity of metallized circuits that use thick-film conductors or frits on ceramic substrates such as molydenum, "moly-mag," tungsten and other such materials.
Plating is often used to enhance solderability. Tin, tin-lead, tin-bismuth, various silver alloys, gold and gold alloys, electroless nickel-boron and electroless nickel-phosphorus alloys are common materials for soldering. Each has advantages and disadvantages. Selection is based on the end use of the component to be soldered. For example, burn-in devices must withstand high heat excursion. Diffusion barriers are required where copper, gold or silver is used in the circuit. Diffusion of any of these metals to a service can allow oxidation that alters the desirable characteristics of the device. Even a small amount of diffusion into the plating can alter conductivity. Oxides of copper, silver, nickel and most other metals do not solder well. Copper oxide is a semiconductor that can cause noise in high-frequency circuits. Electroless nickels, electroplated nickel, cobalt and palladium can be soldered if aggressive solder fluxes can be used (RMA or certain organic acids).
Gold is often prescribed for soldering applications. However, it is well known that gold is soluble in most solders, leading to weak, dull solder joints when the level of gold contamination is high enough. If gold is used for soldering or bonding, a diffusion barrier between copper and gold must be used. The gold deposit should be thin, less than 10 micrometers. Using pulse rectifiers, gold deposits can be produced on properly prepared surfaces with little or no porosity, thus allowing the use of thinner deposits. Immersion gold deposits are commonly used over electroless nickel for soldering. Electroless gold has gained popularity because of the ability to plate isolated areas without electrical contact. Electroless gold is difficult to maintain and control to achieve consistent results.
Good diffusion barriers are electroless nickel-phosphorus, electroless nickel-boron, cobalt, and nickel electroplating comes a close second. According to AESF Project 29, electroplated cobalt and electroless cobalt-5% phosphorus and electroless nickel-8% phosphorus performed the best as diffusion barriers. Turn and Owen reported nickel-phosphorus and nickel-boron to be effective barriers after 12 hrs at 550C.
Via-hole filling. Very large-scale integrated circuits (VLSI) use multilevel circuit interconnections to provide high density and reliability in a compact structure. During fabrication, a layer of metallization is deposited on the silicon wafer and the conductors are etch defined. A layer of dielectric is then deposited and windows (via-holes) are etched through the dielectric to connect points on the metallization. The next layer of metallized conductors is then applied to form interconnections. Using this technique, the upper layer is not completely planar because of the depth of the via-holes. This problem is compounded when additional layers are required to complete all interconnections. It is important to have a planar surface topography at all stages of production, or stress, etching irregularities and serious problems in lithographic patterning can result. It is therefore essential to fill the via-holes with a conductor before metallization to produce high reliability interconnections. Vacuum deposition methods have been studied extensively. It has been found that they do not work as well as electroless nickel plating. Electroless processes are simple, low cost and easy to implement.

Ting, Paunovic and Chiu report the following process: 1-micron layer deposited by a sputtering process. Then a 1 to 1.5 micron layer of undoped oxide is deposited by an LTO process. Via-holes of 1.5 microns nominal size are formed by photolithograpy and plasma etching. The aluminum conductor is activated using a light etch to remove surface oxides, followed by DI water rinse and a 40C palladium activation solution. The wafers are rinsed and immersed in a 55C electroless nickel boron plating solution at pH 6. The plating rate was 2.8 microns per hour. For plating onto silicon surfaces, palladium activation is not necessary. Silicon is etched in a nitric acid fluoride salt-water mixture. The pH of the electroless nickel-boron solution is raised to 8, and the temperature is 55C.
Harada, et.al, reported successful via-hole filling using electroless nickel-boron on aluminum conductors patterned on silicon substrates with 600 nm thickness of phosphosilicate glass films deposited for interlayer insulation. Via-holes of 2, 3 and 4 micrometers in diameter were formed using reactive ion etching, activated with palladium chloride and plated with an electroless nickel-born solution. This resulted in a flat, smooth surface with 100% process yield.
Dishon reported that "The electroless nickel deposition process has been applied for the via filling step in the production of a thin-film multichip computer packaging module." Nickel-boron deposits were plated onto evaporated copper on a Si wafer. Cr/Cu/Cr layers were evaporated, coated with a polyimide that was coated with silicon oxide or silicon nitride, patterned and via-holes etched down to the chromium layer. Chromium was removed in hot hydrochloric acid. Activation of the copper surface was done by acid cleaning. An electroless boron-nickel strike activated the copper and electroless nickel-boron plating followed. By activating the copper surface (using the nickel strike), the side was not activated, allowing excellent planarization. Nickel-boron plating was chosen because of its good conductivity, (6 to 9 microohm/cm) lack of noise production, and it is easy to use.
Electroless copper could be used; however, the plating solution is highly alkaline and will attack aluminum, polyimides and other materials. It is difficult to achieve high levels of adhesion of electroless copper to metallic surfaces.
Flip chip devices using electroless nickel and immersion gold have gained popularity. Nickel bumps are formed through various masking techniques then over plated with immersion gold. For wire bonding to these bumps, electroless palladium is plated over the electroless nickel followed by immersion gold.
Corrosion control. Corrosion of electronic components is destructive in many ways. Loss of surface conductivity, increase of contact resistance, deterioration of the components, broken connections, soldering, brazing and wire bonding are made difficult. Failures in dielectric between metal lines due to accelerated corrosion when voltage gradients are applied. Change reported that in the absence of a voltage gradient, corrosion was only just apparent after 2,000 hours, but corrosion was observed within 50 hours with a 25v potential difference between the two conductors 0.5-mm apart.
The corrosion rate increases linearly with increasing potential differential. Selecting the right plated coating will lessen or eliminate corrosion under these circumstances. Electroless nickel phosphorus is a good protector of circuit elements. Electroless nickel, and to a lesser extent electroplated nickel and gold at a thickness to assure the elimination of porosity, serves very well. Tin could migrate under potential differences and offers much less corrosion protection.
Ceramic hybrid's and MCM-C circuits. Metallization materials such as manganese, moly-manganese, tungsten and thick-film material such as silver alloys, copper alloys, etc., all need corrosion protection. Electroless nickels offer excellent protection to all these materials. Combinations of electroless nickel-gold and electroplated nickel-gold offer high quality surfaces. However, a combination of electroplated nickel or electroless nickel-phosphorus plus electroless nickel-boron provides not only corrosion protection, but a solderable, brazable and wire bondable surface. Using electroless nickel-boron, hermetic brazed seals can be accomplished without fear of cracking or leaks.
EMI Shielding. Plated EMI shielding, although not new, is becoming essential to electronic device protection. Plated electroless copper and electroless nickel offer many advantages over conventional shielding. It can be used to plate non-conductors such as various plastics. The plated shielding has the best shielding characteristics of any of the coatings available.
Electronic connectors. Aluminum hermetic connectors require electroless nickel to provide a hard surface for the aluminum and corrosion protection. Plastic connectors are made possible by use of electroless nickel deposits to form a hard electrically conductive surface.
Printed wiring boards (printed circuits) use electroless copper for connecting one side to another. This is called the plated through-hole process. Additive circuits are also made using electroless copper. Electroless nickel has been used successfully for plated through holes and for additive circuits. The advantage of electroless nickel-boron for plated through holes is that smaller diameter holes can be successfully plated where electroless copper often will not completely plate on all surfaces, leaving voids or no connection at all. Eliminating formaldehyde, a hazardous material, is another incentive to substitute electroless nickel. Electroless nickel boron solutions produce a small amount of hydrogen. The gassing draws solution up through the holes and allows uniform deposits. Holes as small as 0.010 inch to 0.5 inch long have been plated with complete connection reliability. Electroless copper failed to connect any of the 300 holes tested. Electroless nickel serves as a good undercoat for all other plating. Plug-in fingers are enhanced in hardness and wear resistance by using electroless nickel and as undercoat for gold. Sliding contacts are made more reliable with electroless nickel undercoating.
Direct plating through holes for two-sided and multilayer printed wiring offers some advantages over the use of catalytic activators and electroless copper. One method uses conductive carbon in the holes followed by copper electroplating, thus eliminating the hazardous chemicals of electroless copper plating.
Plated deposits. Electroplated palladium, palladium-nickel alloys and electroless palladium deposits perform as substitutes for gold plating in some applications. Combinations of palladium and electroless nickel fill other applications where wire bonding, die bonding and soldering are required. Aluminum wire can be bonded to electroless nickel boron without fear of Kirkendall voids or weak bond joints. Ultrasonic bonding with higher energy than is used for gold makes a durable, strong aluminum wire bond. Nickel cannot be thermal compression bonded using the present techniques.
Palladium, palladium nickel alloys and electroless palladium deposits are used for hybrid, DIPs and MCMs for several reasons. An oxide-free surface allows palladium to be soldered and wire bonded easily compared with nickel. A thin (0.025 to 0.05 micrometer) gold over-layer is sometimes used to enhance soldering. The solderability of palladium remains good even without the gold layer.
Tin alloys of lead, bismuth, silver and others also afford some corrosion protection to printed wiring board circuits. What happens to these plated coatings at elevated temperatures? Nickel phosphorus deposits harden considerably beginning at 300C and reach a maximum at about 385C. Oxidation takes place, and the deposit changes in volume and composition. Nickel-phosphorus intermetallic compound forms. Oxidation of both nickel and phosphorus occurs. Above 600C, migration of phosphorus takes place. Above 800C, decomposition and evaporation of phosphorus from the coating occurs. The addition of even a small amount of boron to the deposit decreases the amount of oxidation significantly. Heating nickel phosphorus in air or moist hydrogen to a temperature of 400 to 850C for 10 to 15 min removes the phosphorus from the surface of the deposit, making it much easier to solder, braze, wire bond or die bond. Ohmic contacts are made to thick film layers on ceramic semiconductors by plating electroless nickel and heat-treating.
Gold, silver or platinum thick-films are much more electrically resistant than expected from calculated values. Plating and then heat treating electroless nickel on these films enables the fabrication of stable, low-contact-resistance metal layers. Nickel boron deposits do not need the thermal excursion for die or wire bonding.
Plating metals and alloys never before possible to deposit are made possible using pulse plating rectifiers. Examples are gold iron, chromium iron, cobalt nickel iron, chromium nickel iron, nickel titanium iron and possibly others. Further control of the structure of the deposits is possible. For example, "super lattice" alloys can be produced as well as ductile amorphous alloys. Commonly plated metals benefit by pulse plating in that more uniform electrodeposits are possible for most metals as well as improved ductility and deposit leveling.

source pfonline.com/articles/129901.html

Increasing Plating Flexibility

For 35 years Tomlinson Industries, Garfield Heights, Ohio, has plated with the same continuous fixed-cycle return machine. Recently, it increased its plating flexibility and reduced its reject rate from 10 to two pct by replacing the old equipment with a computer-controlled hoist system.
Tomlinson employs 175 people and is a world leader in the manufacture of liquid-food dispensing valves used in tea, coffee, beer and wine dispensers. The company exports more than 25 pct of its products to 70 countries worldwide. The company holds an E-Star Award from the U.S. Department of Commerce for maintaining its level of export business. Tomlinson is also in the process of obtaining ISO 9000 certification. As part of the process, employees are trained to hand-inspect each valve.
As a captive nickel-chrome plating shop, the company plates more than 1,000 different parts in small quantities. Brass, aluminum and steel are plated at the facility. Brass parts undergo aqueous cleaning, a priming brass soak, secondary brass soak, electrocleaning and an acid salt cleaning. Steel parts have only one soak cleaning, which is followed by an electrocleaning and acid salt cleaning. The aluminum parts are ultrasonically cleaned, soak cleaned, acid salt cleaned and then zincated. All parts receive a nickel strike and are then nickel and chromium plated.
Choosing a New Machine. When the time came to replace the aging return machine, Tomlinson considered three options: purchase a new return machine; purchase a rebuilt return machine; or purchase a computer-controlled hoist system.
After researching all the options, Tomlinson invested in a turnkey plating system from that included a hoist, computer controls, auxiliary equipment and installation. The company designed a new plating room to accommodate the system, which allowed Tomlinson to keep the return machine running until the new system was operational.
Problems with the Return Machine. Ken Sidoti, plant engineer for Tomlinson, cited flexibility as the key factor for replacing the dedicated return machine. Cycle changeover was time consuming and labor intensive with the return machine. Changing from brass to aluminum or steel substrates involved stopping the machine, unloading the parts, manually pretreating them, and re-racking. This transition cycle averaged 20 min.
Computer-Controlled Hoist Offers Flexibility. The Atotech computer-controlled hoist has transition cycles that allow instant changeover from one base-metal cycle to another, with minimum production loss. The machine is programmed to know which parts to pick up and which tanks to put them in, based on operator selection.
"Flexibility and reliability are key to scheduling our jobs," explained Mr. Sidoti. "Now, at the flip of a switch we can changeover to the nickel cycle in eight min rather than 16 min."
Plant Manager Jim Leigh agreed. "One huge benefit is the ability to incorporate a cleaning cycle for the three different base metals into the automatic machine, which results in higher quality parts and a significantly lower scrap rate." An added benefit was derived from the machine because products that were sent to an outside supplier for clear anodizing are now chromium-plated in-house on the hoist system.
Tomlinson expects a three-year return-on-investment, according to Leigh. "This system does everything we asked for. We couldn't be more pleased."
After 35 years Tomlinson decided to make a change and found it to be both flexible and profitable.

source http://www.pfonline.com/articles/069607.html

Nickel Exposures in the Plating Workplace and Environment

Many metals, including nickel, are coming under increasing scrutiny by regulators because of real or alleged effects on the environment and human health. Nickel initially attracted attention because of a greater incidence of lung and nasal cancers among nickel smelter and refinery workers in the early decades of this century. Nickel-containing materials identified with these cancers are nickel oxides and subsulfides and to a lesser extent nickel sulfate. There is no compelling evidence that nickel metal itself causes cancer.
Workers are exposed by inhaling airborne particles, which can remain in the lungs for many years. The dusty conditions that existed in early nickel production operations have been eliminated. Today worker exposure is usually within regulated limits.
In the 1980's, under the leadership of the world-renowned Sir Richard Doll of Oxford University, an international team of epidemiologists conducted a major epidemiological study of early production operations. The data were ambiguous. The most confounding factor was that most of the workers smoked. The so-called "Doll" study concluded there was no evidence to suggest a health problem from insoluble nickel compounds (oxides and sulfides) at nickel concentrations less than 10 mg/cu meter. It also concluded there was no health problem from soluble nickel compounds (sulfate and chloride) at concentrations less than one mg/cu meter.
Most regulated limits today are one tenth of those exposures or less. While some operations occasionally exceed the limits, most are in compliance. Also, there is little evidence today of elevated incidence of lung or nasal cancers among nickel producers or users relative to local populations.
Nickel Dermatitis. The other significant health effect of nickel is dermatitis. This is a phenomenon associated with soluble nickel compounds or nickel metal dissolved in sweat that penetrates skin causing an allergic reaction in genetically predisposed individuals. As a workplace exposure, this is probably a greater risk than is lung cancer by inhalation of aerosols of nickel sulfate, chloride or sulfamate.
As many as 10-20 pct of women and one to two pct of men are nickel sensitive. It is caused primarily by wearing inexpensive, nickel-plated jewelry. Nickel plating is common in jewelry making, but often the nickel is plated with silver, gold, platinum or other noble metals. Inexpensive jewelry simply stops at the nickel plate, and, thus, nickel metal is in direct contact with the skin. If the contact is long enough for sweat to react with the nickel, the dissolved nickel can cause an allergic reaction.
It is important to recognize that it is not nickel metal that is the problem, but rather dissolved nickel. Nickel that is not in contact with the skin long enough to react with sweat is not a problem; nor is nickel in a form that does not react with sweat, such as most stainless steels. While there are problems with inexpensive nickel-plated jewelry, there are seldom problems with stainless steel wrist watches.
Concerns in the Plating Industry. Nickel-platers can get dermatitis from skin contact with soluble nickel compounds. They can experience respiratory problems from inhaling airborne aerosols or other nickel-containing particles. The preventive measures are gloves and ventilation and/or masks.
Gloves are a better preventive than cure for dermatitis. Once sensitized to nickel, gloves may not eliminate the problem because they enhance the generation of sweat, which encourages dermatitic reactions. Some nickel-sensitized workers have ultimately had to change their work functions to eliminate exposure to soluble nickel. As for respiratory effects, ventilation is preferable to a mask, but the latter is an additional safety feature that minimizes exposure.
Exposure Measurement and Data. Nickel exposures in most nickel plating operations are unknown. Most platers feel they simply do not have the resources to measure exposure. Those who do generally buy the service rather than do it themselves.
Details of exposure measurement are extensive and can be found in the "Safe Use of Nickel in the Workplace." This is a health guide published in June 1994, as a joint effort of the Nickel Producers Environmental Research Association (NiPERA) and the Nickel Development Institute (NiDi). The guide is a comprehensive reference to the health effects of nickel and its safe use in the workplace. Included in the guide is a description of devices and procedures for measuring exposure to various nickel-containing substances.
The data from various nickel plating operations show that while exposures exceed regulated limits in parts of some operations, they are generally lower and in compliance with regulated limits overall.
Nickel Exposure Limits. Permissible exposure limits (PELs) are different but similar from one country to another. In the United Kingdom the PEL for nickel metal and all nickel compounds is 0.5 mg/cu meter. There is no distinction made of nickel in various forms. In the U.S. the limits are one mg/cu meter for nickel metal and insoluble nickel compounds and 0.1 mg/cu meter for soluble compounds. U.S. courts required OSHA to rescind the 0.1 mg/cu meter limit because it had been improperly established. Thus the only legally binding PEL for nickel and any of its compounds, except for nickel carbonyl, is one mg/cu meter.
The American Conference of Governmental Industrial Hygienists (ACGIH) has proposed lower Threshold Limit Values (TLV's) that could be adopted by OSHA in 1997 or thereafter. The initial proposal in 1989 stated that the TLV for nickel and all its compounds should be decreased to 0.05 mg/cu meter. This TLV has been consistently opposed by NiPERA and NiDi. As a result, ACGIH has delayed decision on the matter annually since the original proposal.
ACGIH is now thinking of revising its proposed TLV's to 0.5 mg/cu meter for nickel metal, 0.1 mg/cu meter for insoluble nickel compounds and 0.05 mg/cu meter for soluble nickel compounds. While these limits are still unacceptable to industry, they are an improvement over a proposed TLV of 0.05 mg/cu meter for all nickel substances. ACGIH is also likely to propose that nickel and all its compounds be classified as confirmed human carcinogens. Presently this designation applies only to nickel oxides, subsulfides and nickel carbonyl. NiDi and NiPERA feel that, based on the evidence, inclusion of other nickel substances in this category is unjustified.
Risk Assessment. The attitude of this proposal is that if a substance is shown to be hazardous, causing problems under certain imposed conditions, then it should be regulated as though it would cause the same problem under any less severe conditions.
The industrial, and much of the scientific, community promotes an alternative view that regulation should be risk based. This means that under given conditions an undesirable effect actually does happen, not whether it might happen.
As an example: gasoline is a hazardous substance, but its use in automobiles is not a significant risk because it is kept in closed gas tanks. Exposure limits should be set at levels above which it is known there are unacceptable risks, not at lower limits simply because the substance is regarded as hazardous.
The most important information for regulating substances is actual exposure and worker health records. If the health records indicate no elevated health effects relative to the surrounding community, then there would seem no reason to regulate exposures below those that have prevailed in practice. This is the position NiDi adopts with regulatory agencies.
Wastewaters. In addition to workplace exposures, nickel-platers must also be concerned about emissions of nickel-containing gases to the air; liquids to sewers or drains; and solids to recyclers or landfill.
Regulations govern the disposal of aqueous or other effluents to sewers or natural water courses, including nickel. Again, limits vary with jurisdictions and may be more constrained in regions or municipalities than nationally. It is the responsibility of each plater to determine the regulations affecting him. Nickel limits for aqueous effluents presently established by the U.S. EPA are 1.1 mg/liter a day and 0.5 mg/liter a month average. Most plating operations cannot comply directly with effluent wastewater regulations wherever they are. Wastewaters are therefore commonly treated with lime to neutralize and precipitate residual nickel concentrations so that effluents are in compliance.
Solid Wastes. Most of the solid wastes generated by platers are precipitates from aqueous effluents. Characteristically, these are relatively small quantities by weight and volume and are accumulated in drums to be picked up at appropriate intervals by recyclers, disposal agencies or both. They assume responsibility for the environmental fate of the waste either by recycling or disposal. Waste for disposal must either meet leachate tests before going to landfill or discarded at higher cost in hazardous waste landfills.

source http://www.pfonline.com/articles/059606.html

Nickel-Chromium Plating In-House

A car is not simply transportation anymore. A car makes a statement about the driver. And drivers want to make a statement with their cars. Witness the increase in demand during the past four years for chromium-plated wheels. Not just any type of chromium-plated wheels, but ones with intricate, bold and elegant designs.
Most often, these "designer" wheels are added after the car is purchased. Progressive Custom Wheels, Riverside, California, is one of the country's leading suppliers of aftermarket wheels. It designs, manufactures and finishes thousands of wheels each week. This thirteen-year-old company was founded by three men who had been in the wheel business since their careers started: Wallace "Mo" Kreag, Sandy Smart and Larry Kingsland.
The company has since grown to include three plants on 25 acres in Riverside. The company has 60 warehouses around the country where it stocks a multitude of wheel types and designs. The company manufactures four basic types of wheels.

WHEELS processed through the preplate cycle at Progressive Custom Wheel.
The four types include one-piece aluminum, two-piece aluminum, composite wheels (cast aluminum with a steel rim) and a steel wheel with a steel center welded to the rim. Progressive does not cast steel wheels; it only casts aluminum wheels. Also, two-piece wheels are not plated; they are polished and buffed, giving them the look of a plated wheel.
In April of 1997, as part of a cost saving and quality control move, the company brought nickel-chromium plating of aluminum wheels in-house. This was not popular with the neighbors and required much political maneuvering on the part of the company.
To assist with installation and startup, Progressive hired Gary Madrigal to design, engineer and install the four plating lines. Mr. Madrigal designed the layout of the two manual and two automated lines.
The automated lines handle wheels up to 20 inches in diameter by 12 inches wide. Auxiliary anodes are used with about 50 pct of the wheels.
Progressive starts by lowering the aluminum wheels into the Atotech SoakTM 115, a mildly alkaline, low-pH cleaner. Wheels are then etched in Alklean 77, a 100-pct active alkaline etch that contains chelating agents and an inhibitive grain-refining agent. This process produces a uniform stain etch on the aluminum wheels. It can provide a number of decorative finishes simply by controlling the temperature and/or concentration of the bath.
Prior to zincating, wheels are microetched in Alum-Etch-G. The zincate process is Alumseal W-2000. It produces a thin film on the aluminum wheels. It also removes aluminum oxide and applies a zinc film that can be directly plated with copper and/or nickel. Because Progressive double zincates its wheels, the wheels go through Alumseal Activator BD zincate strip.

COPPER-PLATED wheels prior to nickel/chromium plating.Once the wheels are zincated a second time, they go into a nickel strike, Permalume G, which produces a semi-bright deposit over a wide current density range. The finish is highly ductile and has low tensile stress. Following the nickel strike, wheels are copper plated with Cupracid 300. This is an acid copper sulfate process that produces bright, ductile deposits with low internal stress and excellent leveling.
After copper plating, parts are submerged in Trimax 349 alkaline, non-silicated heavy-duty soak cleaner. This removes any grease or oil that may have deposited on the wheels and prevents the dirt from redepositing on the wheels. After rinsing, parts are placed in Trimax 279 CA electro-cleaner, which is a high-performance, high-current-density, reverse-current electrocleaner base. The third cleaner is a mildly alkaline, low-temperature liquid spray cleaner that removes a variety of soils by displacement.
The acid prep step follows. Progressive uses Actisal No. 6, a blend of acid and accelerators. It speeds attack on rust and scale and retards attack on the base metal. The process removes silicate films left by silicate-inhibited cleaners in preceding steps. It also removes smut.
The high-leveling, semi-bright nickel plating process, Niflow, is a non-coumarin containing process. The deposit on the wheels is sulfur free, ductile and intended for use as the initial layer in Progressive's decorative duplex-nickel chromium plating process. The solution is continuously filtered through carbon to minimize contamination. The deposit is relatively bright, even though only a thin layer of nickel is put down.
This is followed by Gemini 850 bright nickel plating process that provides high leveling and good ductility. This nickel process provides a whiter and more brilliant finish.
Microporous nickel is also plated onto the wheels. This process, BNX 600, is a bright nickel plating process with excellent leveling and brightness. It provides a brilliant deposit and good chromium receptivity. The BNX bath uses several additives, including the Clepobrite BNX starter/leveler nickel plating additive, which is a blended two-component system plus a wetting agent. This additive allows for bright plating even in low-current-density areas.
TABLE I—Plating Process for Aluminum Wheels (double rinses between each step)
Process
Temperature
Time
Concentration
ASF
1.
Atotech SoakTM 115
160-175F
3 min
8-10 oz/gal

2.
Alklean 77 alkaline etch
105-115F
1 min
4-6 oz/gal

3.
Alum-Etch-Gmicroetchant desmut
95-105F
1 min
18 pct by volume

4.
Alumseal W-2000zincate process
72F
2 min
55 pct by volume

5.
Alumseal Activator BDzincate strip
75F
1 min
6 oz/gal

6.
Alumseal W-2000
72F
1 min


7.
Permalume Gnickel strike
140-145F
15 min
NiSO4 40 oz/galNiCl2 9 oz/galBoric acid 5.5 oz/galAddition GL-1 5 pct by volumeNickel additive 0.13 pct by volume
20-100 asf
8.
Cupracid 300
78F
60-80 min
CuSO4 30 oz/galH2SO4 7.7 oz/galCl ion 115 ppmBrightener 0.30 pct by volumeLeveler 0.55 pct by volumeWetter 0.30 pct by volume
Cathode 10-60 asfAnode 5-25 asf
9.
Trimax 349soak cleaner
165F
1-5 min
8 oz/gal

10.
Trimax 279electrocleaner
175F
2 min
10 oz/gal
6-12 volts reverse
11.
Spray cleaner
105F
1 min
0.5 to 5 pct by volume

12.
Actisal No. 6
ambient
15-30 sec
10 oz/gal

13.
Niflow semi-brightnickel
140F
60-120 min
NiSO4 40 oz/galNiCI2 7 oz/galBoric Acid 6 oz/galNiflow additive 1 pct by volume
40 asf
14.
Gemini 850bright nickel
143F
20-30 min
NiSO4 35-40 oz/galNiCl2 10-12 oz/galBoric acid 6 oz/galBrightener 2 pct by volumeLeveler 0.1 pct by volume
20-80 asf
15.
Micro-PorousNickel
135F
3 min


16.
Envirochrome 300
115F
3-5 min
Chrome A salts 24 oz/galSO4 0.12 oz/galChromic acid/sulfate ratio 200:1
150 asf
Another additive is the BNX Super Level, which provides fast leveling and a whiter, more brilliant finish.
The chromium plating process employed is Econochrome 300. This is a dual-catalyst chromium plating solution that operates with relatively low metal concentrations. The bath contains a self-regulating catalyst that enhances the action of the usual sulfate catalyst. The finish has excellent color and yields bright deposits over a broad range. The special catalyst simplifies activation of the base nickel on the wheels.
The manual plating lines are used to plate oversize wheels, such as wheels for semi-trucks. It is also used to plate wheels having intricate designs with deep recesses. Mr. Madrigal believes that by using the hand line, you ensure that all areas of the wheel are plated.
The hand line uses McGean-Rohco chemistries. The liquid soak cleaner, LSC-349, is a concentrated detergent for cleaning sisal-buffed steel. It also removes oil, polish, grease and oxides.
The liquid soak cleaner is LEC-279, which contains detergent, alkalis, wetting agent and complexing agents.
The hand line uses the Besplate RLS semi-bright nickel plating process. It is a three-component system that produces sulfur-free, low-stress, ductile and semi-bright nickel deposits that are suitable for mechanical satin finishing or buffing.
The Reflecta single-additive bright nickel plating process that follows provides good leveling, which is needed with the intricately designed wheels. The process also contains a special additive that makes it suitable for plating die cast wheels.
Econo-Chrome 300 is used for chromium plating on the manual lines. The plating system features a special catalyst that gives the plating bath excellent tolerance to dragin of undesirable catalytic ions, such as sulfate.
TABLE II—Manual Nickel/Chromium Plating Line (double rinse between each step)
Process
Temperature
Time
Concentration
ASF
1.
Actisalt
ambient
3 min
8 oz/gal

2.
Besplate R/L/Ssemi-bright nickel
128F
60-120 min

40 asf
3.
Reflecta brightnickel process
140F
20-30 min

Cathode 45 asfAnode 20 asf
4.
Econo-Chrome 300
115F
1-5 min
H2CrO4 20-35 oz/galSulfate 0.11-0.20 oz/gal
100-200 asf
You might think that "mixing" these chemistries from different suppliers would be a problem. Not so for Mr. Madrigal. Mr. Madrigal explained, "It keeps the competition tough and the prices competitive." Also, one has to simply look at the finished product to know that Mr. Madrigal knows how to keep his plating tanks in line.
In addition to plating, Progressive also powder coats wheels. It has a Nordson booth where operators manually apply black powder to specific areas of certain wheel designs.
"We do everything from ingot to the finished product," stated Robert Zimmer, vice president of manufacturing. Any design, any style, any finish you could want in an aftermarket wheel, Progressive Custom Wheel makes it. The company's ability to create and finish a variety of designs allows each driver to "customize" his ride.

source http://www.pfonline.com/articles/049803.html

Anodizing Influences

Many industrial and consumer products are anodized to provide corrosion resistance and/or a decorative finish to aluminum and aluminum alloys. The anodizing process normally involves a series of steps, including emulsion cleaning, inhibited alkaline cleaning, chemical etching, desmutting, anodizing and coloring. Each of these steps is followed by a rinse. The equipment used during anodizing includes processing tanks, DC power supplies, cathodes to improve coating quality, heat exchangers for bath temperature control and racking systems.
The quality of the anodized coatings is greatly influenced by the aluminum alloy used and by the process conditions. The racking system also affects the coating. An attempt has been made to improve the shortcomings of racking systems.
Rack material. The most commonly used rack materials are commercially pure titanium and aluminum alloys.

PIN rack
Commercially pure titanium racks are made of hot-rolled strips with 98.6 to 99.5 pct titanium, small amounts of iron and interstitial elements of oxygen, nitrogen, carbon and hydrogen. High interstitial content increases the strength and lowers the electrical conductivity. High oxygen can produce a hard brittle surface layer, and high hydrogen can lead to embrittlement or failure in service. ASTM Grade 3 annealed titanium has 65-ksi tensile strength, 55-ksi yield strength and holds its strength up to 400F. The modulus of elasticity is 16 x 106 psi. Pure titanium can be bent through an angle of 125 degrees around a diameter of normal thickness without cracking.1
Titanium is a noble metal with a zero to 0.5v electrode potential (in reference to a standard electrode). It is not attacked by sulfuric acid baths and is chosen as a racking material because of its good corrosion resistance and strength. Because aluminum is an active metal, the contact areas between titanium racks and aluminum could cause galvanic corrosion and local defects during anodizing. Titanium racks are best used for anodizing tubular-shaped products or those with holes.
Aluminum alloys commonly used for racks are 6063-T6 and 6061-T6 extruded alloy strips or wires. Alloy 6063 contains 0.7 pct magnesium and 0.4 pct silicon. T6 temper alloys require a 35-ksi tensile strength, 30-ksi yield strength and a 10 x 106-ksi elastic modulus. Alloy 6061-T6 has 1.0 pct magnesium, 0.6 pct silicon, 0.3 pct copper and 0.2 pct chromium. It has a 45-ksi tensile strength and 35-ksi yield strength.1 The machinability of aluminum alloys are high (300) compared to titanium (40). Aluminum alloys can easily be bent and provide easy loading and unloading of parts. Also, aluminum is a highly conductive metal compared to titanium.2

DISC rack
Aluminum alloys have a -0.83v electrode potential, are active metals and dissolve during anodizing. Aluminum racks anodize along with the workpieces and require stripping before reuse. However, they are considerably less expensive to manufacture, provide easy loading and unloading and have high current efficiency. They do have shorter service life compared to titanium racks, however.
Rack design. The racks used for anodizing generally consist of a spine and pins or discs attached to the workpieces. The spine is a strip with a hook at one end. It should be large enough to carry sufficient current to the work pieces. Pin racks normally contain at least two pieces per part with 0.5 to one inch of spacing to accommodate up to 100 parts per rack.
One of the requirements of rack design is that the rack should hold the workpieces rigidly and not allow them to fall off during anodizing. The deflection and stresses of pins and fingers to hold a workpiece can be estimated. Assuming two fingers with a cross section of 0.3 by 0.03 inch and 2.75 inches long, each deflected by D inches by a force, F, with an angle effect d of 8.14 inches, the firmness of holding the part (stiffness K) is given by the relation:
K = F/D = 3EI/dL3
where I is the moment of inertia (bt3/12 = 0.6975 in4) and F is one lb.
For aluminum fingers, E is 10 ×106 psi, K is 2.8 psi, D is 0.35 inches and the holding stress, s, is MC/I or 37,600 psi. In this case, the deflection of the fingers is high (0.35 inches). Because the holding stress of 37,600 psi is above the yield strength for 6061-T6, the fingers will be permanently deformed.
For titanium fingers, E is 16 × 106 psi, K is 4.45 psi and D is 0.22 inch. In this case, deflection of the fingers is low (0.22 inches). The holding stress is 37,800 psi, which is below the yield strength of titanium. This means there will not be any permanent deformation of the fingers.

ALUMINUM alloy parts on rack and enclosed by rack cover
Rack cover design. Aluminum pins and fingers with low stiffness have a tendency to loosen, causing the workpieces to fall off the racks during anodizing. Their recovery from the bottom of the tank is difficult. For chemical film finishing and anodized coatings using a paint base, surface blemishes are not critical. Flexible bags may be tied to the racks to catch the falling parts. The contact of the bag surface with the anodized coating can cause local defects. This is not acceptable for precision anodizing of aluminum parts. For these applications, a rack cover has been developed.3
The rack cover is made up of a cylindrical body, a base with a stiffener ring and support strips with wire hooks to attach the cylindrical body to the spine. The cylindrical body is made of thermoplastic netting, which is resistant to acid baths, alkaline cleaners and temperatures as high as 225F. The diameter of the cylindrical plastic netting is 15 inches or more. It is about 0.015 inches thick with 0.375-inch hole size. It is difficult to weld the netting to the base and have sufficient weld strength. Therefore, plastic ties attach the netting to the base and the stiffener ring. The cylinder is hung to the support strips at the top with hooks.
Because anodized coatings are priced at a fraction of the cost of finished aluminum parts, their loss during anodizing can cause a decrease in production while looking for the lost part. The rack cover has no current interference, is light, does not float and has easy-to-handle attachments for shop use.

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Controlling Electroless Nickel Baths

Every plating process requires and benefits from process control. This is especially important when working with electroless nickel (EN) systems, since control is vital to achieve the desired properties. The most common performance criteria are based on specific deposit properties. Most commonly desired deposit properties include corrosion resistance, hardness and wear resistance.
Achieving desired performance standards depends on whether the proper EN system was originally chosen. Also, correctly operating that system dramatically affects the final deposit quality. All EN systems are similar in this respect. The chemistry, operating parameters, surface preparation and equipment considerations are the primary variables that influence deposition rate, coverage, adhesion, smoothness, uniformity and brightness.
Maintaining an EN solution begins with an understanding of important chemical and physical process variables that influence the solution's performance. These variables directly affect the final deposit quality. The three primary areas include the chemical balance, the interaction of rate and loading effects and the influence of the process equipment on the final quality.
Chemistry and chemical balance. Anyone can make up an EN solution, but successful plating only occurs if the solution is properly maintained. The proprietary systems available today are easy to make up and maintain. There are also standard formulations that allow the user to make up his own system.1, 2 Initially, those who make up home-brew solutions have good success producing acceptable deposits. The challenge is to maintain that level of quality throughout the bath life. Self-prepared solutions often have reduced bath life and are routinely waste treated at one solution turnover or less. The key to a successful EN system is proper replenishment. The chemical balance of any EN bath is critical. Neglecting replenishment schedules or maintenance of solution levels can cause non-uniform deposits, premature bath decomposition, slow deposition rates, poor adhesion, poor brightness, pitting or roughness. Usually, the effects of poor bath control are seen immediately after the parts have been plated. Often, the results of poor bath control are seen in substrate corrosion after the parts have been shipped to the end user.
Table I shows the primary components that make up a typical EN system. The balance and control of these constituents are required for a successful operation. Control can become more difficult due to unusual circumstances found in every process line.
TABLE I—Typical EN Bath Components
Component
Function
Nickel SaltsSulfate, Sulfamate, Chloride
Source of nickel
ReducerHypophosphiteBoranes (DMAB)
Reaction energy source for nickel to be available for reaction. "The Chemical Rectifier".
Chelators/complexorsCitric acid, Lactic acid, Malic acid
Allows controlled amount of nickel to be available for reaction. Avoids a runaway reaction.
BuffersBorate, Acetate, Succinate
Inhibits dramatic pH changes
pH regulatorsAmmonium hydroxidePotassium carbonateSulfuric acid
To adjust and maintain the operating pH
StabilizersMetallic - Pb, Sn, MoOrganic - S Compounds
Plating rate control and prevent uncontrolled plate out
Wetting Agentsbubble release and reduces pitting
Controls solution's surface tension and H2
With a variety of chemical materials comprising these systems, an imbalance will likely cause some negative result. Proprietary systems are usually balanced to maintain the proper chemical ratios if replenishment schedules are followed. Some proprietary systems are easier to operate because of variations in the chemical mix in the replenishments. Some slight modifications of these replenishment systems are common, depending upon specific circumstances related to a particular process line. For example, in barrel EN plating applications, the makeup component containing primarily complexor materials should be added back to the solution during replenishment to compensate for dragout losses. A reduction in the quality of deposit brightness, smoothness obtained or solution life usually occurs if the addition is not performed. The EN chemistry supplier should be consulted for specific replenishment recommendations.
Stabilizers. EN systems have small, ideal concentration levels and tolerances for some of the chemical they use. Stabilizers and brighteners are a good example of these, since they are usually found in the mg/liter range. As shown in Figure 1, stabilizers are important in regulating the plating rate while also preventing the solution from spontaneously decomposing. Keeping the solution level at a nickel concentration above 80% nickel activity is important, because the stabilizer additives may be only 30 to 60% of optimum levels in solution at lower nickel concentrations. This will affect the deposition rate, deposit coverage, brightness and solution stability. Because of how replenishment components are formulated, making large nickel replenisher activity additions of 20% or higher at one time will cause stabilizer and brightener concentrations to be at 120 to 160% of optimum levels. If large additions are made, the solution will be out of balance, and the bath's performance and deposit quality will be poor. Higher than optimum stabilizer and brightener levels cause voids, pits or skip plating, especially around sharp outer corners and edges. The metallic materials used as stabilizers are catalytic poisons at higher concentrations. In extreme cases, they will cause the plating reaction to stop.
Stabilizers are adsorbed on surfaces to be plated in tiny, scattered sites. The adsorption, in small amounts, helps accelerate deposition. Because the stabilizers are diffusion controlled, the more solution that passes over a surface, the more stabilizer can be adsorbed at that location. The edges of the work are the first locations where stabilizers are introduced due to agitation patterns. Under conditions of high agitation, low loading and high or normal stabilizer concentrations, too much stabilizer is adsorbed on the surface of the work producing too many active sites. This poisons deposition in those areas.
Nickel controls. As the nickel concentration decreases, the rate of nickel deposition decreases. A decreasing nickel concentration affects the coverage, brightness and uniformity of the deposit through a reduction of the plating rate or initiation of plate. In order to maintain these properties at an optimum level, small frequent additions should be made. In addition to stabilizer effects that can result, large chemistry replenishments tend to shock the solution, possibly resulting in salt precipitation (whiteout), deposit porosity and roughness, especially in aged baths.

Controlling EN Baths requires regular lab analyses.
Nickel concentration is determined by simple chemical analysis. A small sample of the solution is cooled to room temperature and analyzed with a standardized EDTA solution. The results can be expressed in percentage nickel activity. The optimum level for most EN systems is six g/liter nickel metal, which is equal to 100% activity. In most proprietary systems, the nickel analysis is also used to measure (or gage) the reducing agent, stabilizer, complexor and brightener additive concentrations. The consumption of these materials is predictable, but they are not always consumed at the same rate as nickel. In some situations, separate analyses and adjustments may be required to bring the solution into balance.
Maintaining the tank's solution level, in addition to sampling the solution before analysis, is critical. Also, the effect the tank's solution has on quality is often underestimated. When the solution is heated, water evaporates. Evaporation accelerates if the solution remains heated and at the operating temperature without working or replenishing the solution. Improper maintenance of the solution level through water additions allows all the chemical constituents to appear more concentrated. For example, a six g/liter nickel level may be 6.8 g/liter or higher as water evaporates. The concentration of all other chemicals will also be greater than the optimum level as water evaporates.
It is important to constantly maintain the proper solution volume, especially before plating or taking samples for chemical analysis. An overflow weir in the plating tank helps maintain a constant level that will minimize control problems.
Hypophosphite. The reducing agent is consumed both productively and non-productively during plating. The reducing agent influences plating efficiency. During plating, the sodium hypophosphite reducing agent, "the chemical rectifier," is consumed in a given ratio to the nickel metal during plating. The hypophosphite to metal ratio varies with proprietary systems, and specific supplier recommendations should be followed regarding the control. To maintain the proper metal to reducer ratio, the solution should be periodically analyzed and adjusted with hypophosphite. The reducing agent is also consumed non-productively through hydrolysis, which occurs when the solution is kept at the operating temperature and not used to plate. To optimize the hypophosphite efficiency, it is important to heat up and cool down the solution quickly while maintaining a constant process load in the tank when the solution is heated.
A reaction by-product formed during plating is orthophosphite, a salt that builds up in the solution. The build-up increases the density of the solution, which causes a reduction in the solubility of other components and reduces the plating rate. As the orthophosphite level increases, the deposit smoothness, brightness, plating rate and adhesion can be affected. Often, deposit roughness, pitting or porosity occur.
The steady increase of orthophosphite content is easily monitored by measuring the specific gravity of the solution at a constant temperature, usually room temperature. The orthophosphite content can be used to track the effective bath life and predict when, under normal operating conditions, the solution should be exchanged for a fresh solution. This effectively measures solution dragout or other solution losses on a production scale. Under laboratory conditions, where solution dragout can be controlled, the economical point at which to dump a solution is usually between six and eight metal turnovers. This is the point at which the least soluble salts begin to precipitate from solution. The solution becomes turbid or milky, producing poor quality deposits. There is little economical advantage to stretching the life of an old solution that becomes more difficult to control and maintain.

Close Up view of automated EN line.
Contamination. The concentration of trace metals and other contaminants within the plating solution will affect deposit quality and appearance. Some metals may also tend to act as stabilizers and/or catalytic poisons that inhibit plating. Elements that act as stabilizers include sulfur, cadmium, bismuth, antimony, mercury, lead, zinc and iron. Sources of organic contamination include masking agents, oils, plasticizers from hoses and liners, airborne organic materials and silicates. Nitric acid contamination from stripping the EN tank slows the plating rate, increases deposit porosity and may cause black-streaked deposits. Excessive nitric contamination also results in poor adhesion of EN to the substrate. Poor adhesion occurs because the nickel deposit initiation is interrupted or slowed due to passivation or smut formation on the substrate's surface.
Nitrate test papers are a good tool to verify nitric contamination prior to making up a new EN solution. Neutralizing a tank with ammonium hydroxide or caustic soda does not ensure that all nitrate residues are eliminated from solution. When nitric acid is introduced to the EN solution as a contaminant, it exists as the anions of nitrate and nitrite. As little as one to two mg/liter of nitrite, which is stronger acting than nitrate, become a very strong stabilizer or poison in the EN solution. One to two grams of sulfamic acid added to a nitric contaminated EN solution react with nitrite to produce nitrogen gas that is evolved over time. To prevent the effects of nitric acid contamination, it is good practice to use a final rinse of sulfamic acid in the EN tank prior to making up a new solution. Use nitrate test papers to confirm the cleanliness of rinse tank and filtration systems before mixing a new EN solution. There are proprietary mixes that do not contain nitric acid for stripping EN tanks. In addition to safety issues, these types of proprietary mixes offer other advantages over nitric acid.
Operating pH. The solution's operating pH is an important parameter because it affects the plating rate and the amount of phosphorus co-deposited. Higher pH values favor lower phosphorus contents in the deposit while increasing the plating rate. Higher pH values, within the range for the particular system used, can lead to precipitation of metal hydroxides or orthophosphites. This precipitation normally causes porosity, which affects corrosion resistance.
Lower operational pH levels increase the phosphorus content in the deposit while decreasing the plating deposition rate. Slower plating rates due to operation at reduced pH produce less porous, more corrosion resistant deposits. Unlike electrolytic nickel plating, it is normal for the EN solution pH to decrease as plating continues. Many proprietary systems are self-regulating with respect to pH. Large fluctuations in operating pH are usually an indication of some process problem. Insufficient rinsing of work, which results in contaminant dragin, or inadequate replenishment of the maintenance components should be investigated if there is a pH control problem.
The pH is easily checked electromet-rically or with pH papers, providing the pH increments can be read to at least 0.2 pH units. In laboratory studies, the paper value has been shown to vary depending on the brand or type as well as other variables.3 As the solution's salt content increases, the colors of the pH indicators tend to vary. The amount of time the paper is read after immersion in the EN solution must be standardized to obtain consistent results since color continues to change over time. It is also advisable to calibrate the values obtained by paper with a pH meter for more consistent results. When using the electrometric pH meter you must calibrate the meter with two buffers that cover the expected range. For the best results, the electrometric pH should be measured on a cooled sample. Most pH probes do not perform well or have a limited life when used at EN operating temperatures of 180F or higher. The use of a fast-flow reference electrode works best for older, high-density EN solutions.
Operating temperature. The temperature of an EN plating solution is one of the most important factors affecting deposition rate. The deposition rate increases as the operating temperature increases, especially as temperatures reach 200F. It is important to have the proper heating system to avoid localized overheating, which can result in bath decomposition or deposit roughness. There is a wide range of plating rates versus operating temperatures for the various proprietary systems. For example, many of the four to six pct phosphorus systems plate at 160F while the 10 to 12% phosphorus systems need a minimum operating temperature of 180F. The deposition rate also has an influence on the deposit smoothness, coverage and adhesion. Too high a deposition rate can result in a rough or pitted nickel-plated surfaces. Too low a deposition rate slows the initiation of the EN on the substrate surface, which minimizes the coverage and resulting adhesion. If the nickel initiation is not quick enough, substrates can be attacked by the EN solution, affecting subsequent adhesion.
Bath loading and agitation. For EN solutions, the plating tank size should be no larger than necessary to meet production needs. If additional production is needed later, additional tanks should be used. It is not recommended to anticipate future increases by using a tank larger than current production requires. Bath loading and agitation have an effect on the deposit quality due to interactions with the chemistry. Figures 2 and 3 show the interaction between stabilizer concentrations with respect to loading and agitation.

2. Deposition stabilizer critical concentration vs. agitation.

3. Solution loading vs. stabilizer concentration.
Loading is referred to as the ratio of total exposed surface area being plated to the volume of solution in the tank. Different deposit characteristics can be obtained depending upon the solution loading. Optimum loading will depend on the type of bath or proprietary formulation. However, 0.3 to 0.8 sq ft/gal is a recommended average loading. As shown in Figure 2, if the work load to solution volume ratio is small (less than 0.2 sq ft/gal), the potential for stabilizer adsorption is greater, especially on edges and sharp geometries of the work. The poor coverage can result in edge pullback, step plating, inconsistency in plate thickness and increased porosity with a decrease in phosphorus content of the deposit. Higher bath loading only presents a problem if replenishment schedules are not kept up or if the solution chemistry fluctuates excessively due to high-volume additions. In many cases, high-bath-loading ratios cause the plating solution volume to grow due to required replenishments. This growth usually requires some solution be decanted to allow for the fresh replenishment. If solution removal is required, additions of the complexor make-up component are required to account for the dragout.
Agitation is important to maintain uniform heating and mixing of the solution. However, higher agitation patterns tend to exaggerate stabilizer edge effects as shown in Figure 3.4 A bath that has optimum loading and normal stabilizer concentration can produce poor quality deposits if the solution agitation is too high. As agitation increases, EN solutions can tolerate lower levels of stabilizer. When stabilizer concentrations are high, or if there is extremely low loading, there is more available stabilizer per area to be plated. Coupled with high agitation, this condition will frequently cause poor quality deposits.
Equipment. The equipment used to plate EN deposits can also affect deposit consistency and quality. Usually, the equipment is the difference between producing good or bad quality deposits. Steady maintenance of the tanks, heating, filtration equipment and racks is critical to success. Equipment materials should be resistant to the EN plating solution and the elevated temperatures used in plating. More importantly, they must be resistant to the solutions used to strip extraneous nickel from the tanks.
The air used to provide solution agitation must be clean and supplied from a non-oil-containing air compressor or blower. Oil cannot be efficiently filtered from compressed air since a portion of the oil remains in vapor form, which passes through the filters. There are filters made that will remove oil, but the expense is not justified compared to low-pressure, oil-free blowers.
Disposable, flexible PVC liners can be used in EN applications. However, caution should be taken when choosing flexible liners. PVC tank liners may cause pitting, non-uniform nickel coverage or other poor quality deposit characteristics.5
The heating systems should be designed to avoid localized overheating of the plating solution, which may lead to decomposition of the chemistry resulting in pitted, rough or porous deposits. External steam heat exchangers are the choice of many shops because they heat up the solution quickly. They also require little space outside the tank, which allows for complete use of the tank area for production. It is important to provide adequate velocity of the EN solution through the heat exchanger to avoid localized overheating. It is also recommended to place the filtration system in the same line as the heat exchanger to filter out particles that may form in the chamber of the heat exchanger.
Continuous filtration of EN solutions is required if optimum results are to be obtained. Particulate solution impurities, such as those introduced from sandblasted substrates or dust, can cause roughness in the final deposit. Most systems use five-micron retention filter media. If plating deposits greater than 25 micrometers, or other critical applications, the solution turnover rate should be at least 10 times/hr through a one micron or less filter retention size.
Adhesion. The importance of pre-plating operations cannot be over-emphasized in regards to EN adhesion to any substrate. Having the best EN system will matter if there is poor surface preparation. Some of the costs include stripping the defective nickel, possibly damaging or etching the substrate. Additional polishing, labor and chemical costs may be required. The surface preparation is said to be a factor in 95% or more of the problems with EN deposit adhesion, smoothness and brightness. The final EN deposit quality is only as good as the quality of the base substrate metal since EN's ability to level imperfections in the base material is poor. Smoother substrates produce smoother EN deposits.
Any defect in the substrate will likely be more visible after the part is plated bright. Few, if any EN systems will cover up base metal problems such as porosity, slivers from machining or polishing patterns. The manner in which the part is stamped, cast or drilled has an impact on the final plated product. Oils or compounds can be embedded into the surface of the part causing dull or non-adherent coatings. Good surface preparation is necessary.
Generally, a newer solution favors good adhesion since there are fewer reaction by-products of sulfate and orthophosphite. The sulfate concentration determines the degree of attack on various substrates at plating initiation. Increasing the orthophosphite concentration slows the plating rate and speed of initiation. These constituents can have an effect on adhesion.
Poor brightness and coverage. The basic EN cycle can be thought of as a series of steps intended to remove contaminants or films from the surfaces of the work. The cycle normally consists of a soak cleaner, electrocleaner and acid activation step. Rinsing is critical in the surface preparation cycle and is often overlooked as a source of problems on the line. Residues from cleaners, acids or other pretreatment steps can create passive areas on the part that will not initiate nickel deposition resulting in poor coverage, pitting or lack of deposit brightness. Sharing common rinses between the soak, electrocleaner and acids will cause deposit or solution performance problems. Detergents (surfactants) designed to clean soils in alkaline cleaner solutions may precipitate or form an oily layer if mixed with an acid rinse solution. Rinsewater temperatures of 60F or less require longer immersion times to assure effective rinsing. Very cold rinses will "setup" certain pretreatment residues on the surfaces of parts rather than removing them. Rinse stages are best if kept at 70F or higher. Air-agitated, counterflow rinses minimize contamination dragin to the EN solution. Process lines that incorporate a pre-dip of carbonate, bicarbonate or ammonium hydroxide prior to entering the EN solution have fewer problems with nickel deposit initiation, coverage, brightness and adhesion.
Performance testing EN solutions. Beaker testing of EN solutions can identify and correct problems. These techniques can be used to determine the plating rate, visualize stabilizer problems or verify solution life. It is important to standardize these techniques to provide reproducible results. However, the parameters can be changed to accomplish specific goals toward identifying a problem. A one liter beaker works well for this application because the narrow neck reduces the evaporation. These beakers are specially suited for bath life studies. A magnetic stirrer hot plate is used to agitate the solution. The test panels chosen can be steel or brass Hull cell panels (267 ml size). Steel panels are normally used to calculate rate and verify stabilizer effects. The brass panels are good to use for identifying pitting, especially for thick deposits. The preparation of these test panels is critical, and the results can be misleading if the panels are not properly cleaned and activated. Nickel wire is used to suspend the panels in the beaker.
With this technique, beaker loading can be varied by cutting the size of the Hull cell panel. Panels can also be bent 90 degrees to verify the effects of upper and lower shelf areas of the panel. Once the loading (area per unit volume in sq ft/gal or sq cm/liter) is chosen, the amount of agitation depends on the purpose for performing the beaker test. Some form of agitation should always be used. Laboratory work has shown agitation effects on the deposit rate and other important deposit characteristics.6 For stabilizer effects, choosing a low load of 0.25 sq ft/gal with moderate to high agitation is a good beginning point. For plating rate determinations, 0.5 sq ft/gal with moderate agitation is a good starting point for beaker testing. Panels can be weighed before and after plating to determine the rate of deposition by the deposit weight-gain method. There are different factors used in the calculation depending upon how much phosphorus is in the EN deposit. This method has been studied and correlates well with actual EN thickness by cross-sectional analysis.7 It is important to maintain the operating temperature within two degrees to ensure consistency and reproducibility of the testing. There can be many variations with these tests. However, they can be very useful to determine the quality of the EN deposit.
Given proper control, EN solutions can provide consistent, high-quality nickel-phosphorus deposits. Controlling the chemistry and operating variables of tank loading, agitation, pH and solution temperature are critical for producing high-quality deposits. The type and condition of the process equipment used, other types of mechanical influences and the surface preparation process are also shown to affect the performance of the EN solution. Paying attention to the details allows a high-quality EN deposit to be produced.

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