A Class Metal Finishers are often asked about the difference between hard chrome and normal chrome plating.
Chrome plating (short for chromium plating) is commonly performed for either decorative or functional purposes. The functional version is referred to as hard chrome plating. In fact, aside from a few practical differences, both types are much the same. The main difference is in the thickness of the chromium material applied.
Standard chrome plating for decorative uses is a much thinner deposit (about one micron) of chromium over the relatively thick layer of nickel plating underneath. Hard chrome, however, is a much thicker deposit of chromium – ranging anywhere from 5 microns to, in some cases, over 3000 microns – depending on the purpose of the coating.
Because it is thicker, Hard chrome plating provides much greater corrosion and wear resistance, which is a benefit for many industrial uses but is overkill and expensive for decorative applications. Hard chrome can be used to build up surface thickness on items that have worn down – for example shafts, bores or tool surfaces. The thicker the deposit, the more uneven the surface dimensions become – thus requiring the part to be re-machined after plating. An alternative to hard chrome, which achieves similar levels of corrosion and wear resistance, but builds up evenly and avoids the need for re-machining is Electroless nickel.
Decorative chrome plating is still a resilient coating. It can stand up to a lot of exposure and last many years. The nickel plating (and to a lesser extent the copper plating) layers beneath the chrome provide a lot of protection and corrosion resistance and, applied properly, will meet the quality and longevity standards for its intended purpose.