Chromium is a silvery white metal with a slight blue color. Its relative atomic mass is 5 1.99, its density is 6.98~7.2 1g/cm3, its melting point is 1875~ 1920℃, its standard electrode potential is 0.74V, and its old "/c"-0.4/.

The hardness of chromium plating layer is high, which can be changed in a wide range of 400~ 1200HV according to different bath components and process conditions. Chromium plating layer has good heat resistance. When heated below 500℃, its gloss and hardness have no obvious change. When the temperature is higher than 500℃, it begins to oxidize and discolor, and when the temperature is higher than 700℃, the hardness begins to decrease. The friction coefficient of chromium plating layer is small, especially the dry friction coefficient, which is the lowest among all metals. Therefore, the chromium plating layer has good wear resistance.

Chromium coating has good chemical stability, and 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 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 reflection ability for a long time, which is better than silver and nickel.

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