posted 04-21-2001 08:45 PM                  

Regards,

-Ben

posted 04-22-2001 09:29 PM                  

This page is intended for those many callers who ask something like: "I need information on chrome plating". It gives a quick introduction for the layperson.

What's the difference between "Chrome Plating" and "Chromium Plating"?

Nothing. Chromium is an element, chrome is just sort of a slang name for it.

So all chrome plating is about the same, then?

No. There are two different general types of chrome plating: "hard chrome plating " (sometimes called "engineering chrome plating") and "decorative chrome plating".

Hard Chrome Plating

Hard chromium plating is just chrome plating, but it is 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 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 it always involves plating nickel before plating the chrome. The chrome plating in decorative chrome plating is exceptionally thin, measured in millionths of an inch rather than in thousandths. It is still a very hard surface, but simple 'anvil' type hardness measurements don't detect the hardness because the anvil just punches through such a thin coating.

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 nickel. The chrome adds a bluish cast (filtering the somewhat yellowish cast of the nickel), and it protects against tarnish, and minimizes scratching. But the point is, without the brilliant leveled nickel undercoating, you would not have a reflective, decorative surface.

Some metals, like zinc die castings, cannot be directly nickel plated but must be copper plated first. Other materials, like aluminum, cannot be copper plated until they have been zincated.

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.

Do it yourself?

Sorry, you absolutely cannot do chrome plating at home, in a garage, or basement. Besides involving all of the steps listed above, you would be dealing with hazardous and carcinogenic chemicals. You need exhaust systems, fume scrubbers, and a waste water treatment system. Naturally, you need a host of permits. Even for a very small operation you would need a budget of $100,000 or more.

The way to chrome plate something is to take it to a chrome plating shop :-)

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