Chromium plating is an electrolytic process that is similar to electrolytic copper and nickel plating. Chromium plating serves 2 distinct functions: both decorative and industrial purposes.
Decorative
With a pleasing blue-white finish with high reflectivity, chromium plating adds style to decorative-protective systems. Chromium is seldom deposited directly on the base of the material. It is usually deposited to a thickness of about 0.75 µm (microns) on a nickel or copper-nickel undercoat.
Industrial
Chromium plating is also used for industrial purposes as it able to provide the hardness, corrosion and wear resistance needed in many components subjected to dynamic and environmental forces. Chromium plating in this case would be heavier and usually done with a matt finish, hence giving rise to the name Hard Chrome Plating.
Why Hard Chrome Plating?
Below are the benefits attributed to Hard Chrome Plating. Do note that the figures represented are an estimate and differences could arise due to the differing nature of plating baths used by electro-platers.
Restoration of dimensional tolerances - Dimensions of parts that have gone through wear and tear or can be restored, thereby improving the life expectancy of the plated parts. The extent of restoration, however, can be limited by the severity of wear and the condition of the base material.
Hardness - Its strength would significantly Increase to typical values of 60 HRC
Low fiction - The coefficient of friction for Chrome on steel is 0.16 compared to steel on steel being 0.3. The reduction in friction would thereby improve the wear life expectancy of the plated parts.
Wide temperature range for service applications - Chromium plated parts can usually withstand heat of up to 400°C without any change in its properties. There could be some reduction in hardness and abrasion resistance when the temperature increases beyond 400°C.
Improved chemical resistance - Chromium plated parts can withstand most organic acids, gases and petroluem products. It is however susceptible to chlorides and strong acids.
Lubricant retention - Microcrack characteristic allows oil retention thereby improving lubricity of the plated parts.
