Hard Chrome Plating
Most lay people would not be familiar with hard chrome plating. Hard chromium plating is simply chrome plating applied as a fairly heavy coating (usually measured in thousandths of an inch) for wear resistance, lubricity, oil retention, and other 'wear' purposes. Some examples would be hydraulic cylinder rods, rollers, piston rings, mold surfaces, thread guides, etc. It is called hard chromium because it is thick enough that when a hardness measurement is performed the chrome hardness can actually be measured. It is almost always applied to items that are made of steel. It is metallic in appearance but is not really shiny or decorative.
There are variations even within hard chrome plating, with some of the coatings optimized to be especially porous for oil retention, etc.
Many shops who do hard chromium plating do no other kind of plating at all, because their business is designed to serve only engineered, wear-type, needs.
Decorative Chrome Plating
Decorative chrome plating is sometimes called nickel-chrome plating because bright chrome plating always involves plating nickel before plating the chrome. The nickel provides the reflectivity and most of the corrosion resistance. The chrome plating is exceptionally thin, measured in millionths of an inch rather than in thousandths
When you look at a decorative chromium plated surface, such as a chrome plated wheel or truck bumper, most of what you are seeing is actually the effects of the nickel plating. The chrome adds a bluish cast (compared to the somewhat yellowish cast of nickel), protects against tarnish, and minimizes scratching. But the point is, without the brilliant leveled nickel undercoating, you would not have a reflective, decorative surface.
There is no such thing as "decrotive" chrome plating. That was just a misspelling that has taken on a life of its own.
"Triple Chrome Plating", "Double Nickel-Chrome"
As mentioned, decorative chrome plating always involves at least two layers of plating--a layer of nickel and a layer of chrome. High quality plating requires a minimum of two layers of nickel. There will often be a layer or two of copper underneath the nickel. If the parts are plastic, there will be electroless nickel under that. If the parts are aluminum, there will be a zincate layer first, etc.
Salespeople are always looking for advantage, and will use any good-sounding terms they can get away with. There are no laws that define what triple chrome plating actually means, so salespeople will be prone to call their service "triple chrome plating" if there are a total of 3 layers of any kind of plating, or "quadruple chrome plating" if there are 4. So the terms don't mean much, although they should.
Perhaps the most important issue here is that quality chrome plating (for outdoor exposure such as on a vehicle) must have at least two layers of nickel plating: semi-bright nickel followed by bright nickel. The reason for this involves galvanic corrosion issues. The bright nickel is anodic to the semi-bright nickel, sacrificially protecting it, spreading corrosion forces laterally instead of allowing them to penetrate. OEMs require very close control of this factor, and there is a test (the Chrysler developed STEP test) which large shops routinely run to insure the right potentials. Control of this issue is probably the principal reason today's chromium plating greatly outlasts the chrome plating of earlier times. Experts argue whether copper plating provides additional corrosion resistance or not, but with or without copper plating underlying the nickel, chrome on top of a single layer of nickel will not hold up to severe exposure.
Chrome plating is hardly a matter of dipping an article into a tank, it is a long involved process that often starts with tedious polishing and buffing, then cleaning and acid dipping, zincating, and copper plating. This may be followed by buffing of the copper, cleaning and acid dipping again, and plating in two or three different types of nickel plating solution, all before the chrome plating is done.
Restoration Work
When an items needs "rechroming", understand what is really involved: stripping the chrome, stripping the nickel (and copper if applicable), then polishing out all of the pits and blemishes, then starting the whole process described above.
Most lay people would not be familiar with hard chrome plating. Hard chromium plating is simply chrome plating applied as a fairly heavy coating (usually measured in thousandths of an inch) for wear resistance, lubricity, oil retention, and other 'wear' purposes. Some examples would be hydraulic cylinder rods, rollers, piston rings, mold surfaces, thread guides, etc. It is called hard chromium because it is thick enough that when a hardness measurement is performed the chrome hardness can actually be measured. It is almost always applied to items that are made of steel. It is metallic in appearance but is not really shiny or decorative.
There are variations even within hard chrome plating, with some of the coatings optimized to be especially porous for oil retention, etc.
Many shops who do hard chromium plating do no other kind of plating at all, because their business is designed to serve only engineered, wear-type, needs.
Decorative Chrome Plating
Decorative chrome plating is sometimes called nickel-chrome plating because bright chrome plating always involves plating nickel before plating the chrome. The nickel provides the reflectivity and most of the corrosion resistance. The chrome plating is exceptionally thin, measured in millionths of an inch rather than in thousandths
When you look at a decorative chromium plated surface, such as a chrome plated wheel or truck bumper, most of what you are seeing is actually the effects of the nickel plating. The chrome adds a bluish cast (compared to the somewhat yellowish cast of nickel), protects against tarnish, and minimizes scratching. But the point is, without the brilliant leveled nickel undercoating, you would not have a reflective, decorative surface.
There is no such thing as "decrotive" chrome plating. That was just a misspelling that has taken on a life of its own.
"Triple Chrome Plating", "Double Nickel-Chrome"
As mentioned, decorative chrome plating always involves at least two layers of plating--a layer of nickel and a layer of chrome. High quality plating requires a minimum of two layers of nickel. There will often be a layer or two of copper underneath the nickel. If the parts are plastic, there will be electroless nickel under that. If the parts are aluminum, there will be a zincate layer first, etc.
Salespeople are always looking for advantage, and will use any good-sounding terms they can get away with. There are no laws that define what triple chrome plating actually means, so salespeople will be prone to call their service "triple chrome plating" if there are a total of 3 layers of any kind of plating, or "quadruple chrome plating" if there are 4. So the terms don't mean much, although they should.
Perhaps the most important issue here is that quality chrome plating (for outdoor exposure such as on a vehicle) must have at least two layers of nickel plating: semi-bright nickel followed by bright nickel. The reason for this involves galvanic corrosion issues. The bright nickel is anodic to the semi-bright nickel, sacrificially protecting it, spreading corrosion forces laterally instead of allowing them to penetrate. OEMs require very close control of this factor, and there is a test (the Chrysler developed STEP test) which large shops routinely run to insure the right potentials. Control of this issue is probably the principal reason today's chromium plating greatly outlasts the chrome plating of earlier times. Experts argue whether copper plating provides additional corrosion resistance or not, but with or without copper plating underlying the nickel, chrome on top of a single layer of nickel will not hold up to severe exposure.
Chrome plating is hardly a matter of dipping an article into a tank, it is a long involved process that often starts with tedious polishing and buffing, then cleaning and acid dipping, zincating, and copper plating. This may be followed by buffing of the copper, cleaning and acid dipping again, and plating in two or three different types of nickel plating solution, all before the chrome plating is done.
Restoration Work
When an items needs "rechroming", understand what is really involved: stripping the chrome, stripping the nickel (and copper if applicable), then polishing out all of the pits and blemishes, then starting the whole process described above.
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