Have you ever wondered what’s the difference between decorative chrome or hard chrome plating?
Chromium is about the same hardness in both decorative chrome and hard chrome plating, about 800 to 1000 VHN (which is incredibly heavy). The main difference is found in the thickness of the deposit.
For the decorative purpose of chrome, it is seated best on nickel, which adheres incredibly well to copper – the combination of all three offers possibly the best corrosion protection resistance available. Decorative chrome thickness can vary from anywhere between a few hundredths of a mil to one mil. The mirror finish will effectively only be as good as the finish that is on the surface before the chrome, so it’s all a very difficult process at times.
For the purpose of being functional, or take either take advantage of the extremely low friction that chrome holds or for building surfaces and pistons, hard chrome will be plated with a thickness anywhere between 1 to 50 mills.
When used as a bearing surface, chrome simply must be micro-finished, something which will then provide a level of friction much lower than any other metal when used against the likes of steel, iron, brass, bronze or aluminium alloys. There’s something that you mustn’t do; Do not use chrome against chrome. Chrome is much harder than casehardened steel, so we are then left with a perfect set-up for longwearing working surfaces. Chrome will resist pretty much all organic and inorganic compounds and acids, except hydrochloric acid.