Usually, our customer will request us to apply chrome plating service on the polished steel parts. Chrome plating is the process which electroplates a thin chromium layer on other metals.

The chromium-plated layer has a very high hardness, and its hardness can vary in a wide range(400-1200HV). Which is depending on the composition of the plating solution and process conditions. The chromium-plated layer has a good heat resistance. When it’s heated and the temperature is below 500℃, the gloss and hardness of chromium coating won't have obvious change. When the temperature above 500℃, it will start to oxidize and discolor. And the hardness of the chromium coating will start to decrease when the temperature exceeds 700℃. The friction coefficient of the chrome layer is small, especially the dry friction coefficient, which is the lowest one among all metals. Therefore, the chrome-plated layer has good wear resistance.

The chromium plating layer has good chemical stability. The chromium coating has no effect in alkali, sulfide, nitric acid and most organic acids, but it can be dissolved in hydrochloric acid (such as hydrochloric acid) and hot sulfuric acid. In the visible light range, the reflectivity of chromium is about 65%, which is between silver (88%) and nickel (55%). Because chromium does not change color, it can maintain its reflectivity for a long time,  which is better than silver and nickel. 

There are two types of chrome plating, one is decorative chrome and the other is hard chrome plating.

Decorative chrome plating 1-3μm

Wear resistance chrome plating/ Hard chrome plating 50-100μm

Protection-decorative chromium plating: Protection-decorative chromium plating is commonly known as decorative chromium. The plating layer is thin, bright and beautiful. Usually, the decorative chromium is used as the outermost layer of multi-layer electroplating, for the protection purpose. 

A thick enough intermediate layer must be plated on the zinc base or steel substrate first, then plate a thin chromium layer of 0.25-0.5μm on this bright intermediate layer.

The polished product can obtain a silver-blue mirror luster if  the surface plated with decorative chrome. And it can be exposed in the atmosphere for a long time, without color changes. This type of coating is widely used in the protection and decoration. Such as the parts of automobiles, bicycles, sewing machines, clocks, instruments, and daily hardware etc.

Cosmetic Chrome Plating

Hard chromium plating (abrasion-resistant chromium): It has extremely high hardness and wear resistance, which can extend the service life of workpieces. Such as cutting and drawing tools, pressing molds and casting molds of various materials, bearings, shafts, gauges, gears, etc. Hard chromium plating can also be used to repair the dimensional tolerances of worn parts. Generally, the thickness of hard chromium plating is 5-50μm, but it can also be determined according to needs. Some of them could be as high as 200-800μm.

Hard Chrome Plating

Black chrome coating: Which has a black color, uniform gloss, good decoration, good matting and high hardness (130-350HV). And the wear resistance of black chrome coating  is 2 to 3 times higher than bright nickel at the same thickness; The corrosion resistance of black chrome plating is same as the ordinary chrome plating, and which mainly depends on the thickness of the intermediate layer. Black chrome coating has good heat resistance and will not change color below 300°C. The black chromium layer can be  plated on the surface of iron, copper, nickel and stainless steel directly. If it's necessary to improve the corrosion resistance and decorative effect, some alloys can also be used as the bottom layer. Such as copper, nickel or copper-tin, and the black chromium plating layer can be plated on the surface of these alloys. Black chrome coating is often used for the protection and decoration,  such as the parts of aeronautical instruments  optical instruments, solar absorption panels and daily necessities.

Black Chrome Plating