Hard Chrome plating – or Decorative chrome?
What is the difference between hard chrome and normal chrome plating? Here’s a brief overview.
Chrome (short for chromium) plating is commonly performed for either DECORATIVE or FUNCTIONAL reasons. The functional version is referred to as HARD chrome. Actually, as far as plating solutions and technologies go – aside from a few practical differences – both types are much the same. The main difference is in the THICKNESS of the chromium material applied. Heat treatment also plays a role in some applications.
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. The hard version, however, is a much thicker deposit of chromium – ranging anywhere from 5 microns to, sometimes, over 3000 microns – depending on the purpose of the coating. (A micron is equivalent to one millionth of a metre, or, one thousandth of a millimetre. In inches there are about 25 microns to one thousandth of an inch)
Because it is thicker, Hard Chrome provides much greater corrosion and wear resistance, which is a benefit for many industrial uses but is overkill and expensive for decorative uses. It 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, that achieves similar levels of corrosion and wear resistance, but builds up evenly, (thus avoiding the need for re-machining) is Electroless nickel.
Decorative chrome plating is still a resilient coating, it can certainly stand up to a lot of exposure and last many years (example – plated chrome parts on cars or motorcycles). The nickel plating (and to a lesser extent the copper plating) layers beneath the chrome provide a lot of protection or corrosion resistance and, applied properly, will meet the quality and longevity standards for its intended purpose.
Please contact the electroplating team at “A Class Metal Finishers” if you need more detailed information about any plating process.
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