Electroplating refers to a surface processing method in which the cations to be plated in the plating solution are deposited on the surface of the base metal by electrolysis with the base metal to be plated as the cathode in a salt solution containing the metal to be plated to form a coating. The performance of the coating is different from that of the base metal and has new characteristics. According to the function of the coating, it is divided into protective coating, decorative coating and other functional coatings.