Chromium Plating

Hard Chromium plating is the name adopted by industry for what might be better termed chromium plating for engineering rather than decorative purposes. There is no evidence that ~hard" chromium is necessarily any harder then decorative chromium.

The solutions used in both types of chromium plating are the same. The concentrations of these solutions is also about the same. Since deposits are usually much heavier in non decorative uses, the plating times are much longer and a knowledge of plating speed is necessary'.
Chromium as a surface finish offers a rare combination of physical and mechanical properties: low coefficient of friction, high hardness, good corrosion resistance, high heat resistance, and anti-galling properties.

Lead anodes are used or lead with up to 10 percent tin or antimony. When plating complex shapes, anodes can be used in wire form for conforming to the shape of the cathode.

The principal way in which hard chromium plating differs from decorative is that the deposits are usually much thicker and their physical properties much more important. As a rule, the product is destined for rough usage: slight errors that might be tolerated in decorative plating cannot be permitted. The parts being plated are often large and valuable: rejects can be catastrophic rather than simply annoying. Since plating times are much longer, proper conditions must be maintained over longer periods, which requires better control and more careful monitoring.

Because of its low coefficient of friction against other materials, its utility is excellent in shafting, piston rings, internal-combustion-engine cylinders, and similar uses. Chromium plate, however, generally reduces the fatigue strength of steels upon which it is deposited~ shot peening and other methods of preparing the steel for plating can reduce this effect. Heat treatment after plating can also be useful.