Keith covered it well. And hardchrome is definitely applied using the identical physics of electro-plating car bumpers. Car bumpers get "triple chrome plating" as Keith described, which is three different metals. The copper is plated thick so it can be buffed and flowed to form a smooth surface. The nickel plate provides the most corrosion resistant protection. The chrome is decorative. Hard chrome can be plated thin or built up. Airplane piston engines sometimes use the process to rebuild cylinders to original bore size by first grinding the bore oversized, then plating thick hardchrome, then grinding again, honing to final finish. It can flake off in thick applications , like decorative chrome, give similar conditions. I've seen neglected hardchrome cylinders flaking.
Either hardchrome or decorative chrome can be plated directly to the base metal. In the case of decorative chrome, either hexavalent or trivalent, it does not meet the needs of most products to directly plate decorative chrome on the base metal without the finishing aid of copper or the corrosion protection properties of the nickel.
Hardchrome and decorative chrome are not the same metal.
The gold, and other colored, coated drill bits, are a electro vapor deposition of nitrides or carbides, often titanium nitride. They are harder than hardchrome.
Last edited by Chuck H; 07/02/19 12:05 AM.
