Traditionally, chromate passivation is used, and now trivalent chromium passivation or chromium-free passivation is generally used. The recipe is generally not made public.

Passivating liquid is a solution that can make the metal surface passivated. Generally used for post-plating treatment of zinc plating, cadmium plating and other coatings. The purpose is to form a surface state on the surface of the coating that can prevent the normal reaction of the metal, improve its corrosion resistance, and increase the beauty of the product. Through formula analysis, it can be seen that the main components of commonly used passivation solutions are chromic acid, nitric acid, and sulfuric acid. However, due to environmental pollution caused by chromic acid, in some cases, the product is required to be silver-white or blue-white. The rainbow-colored passivation film generated after triacid passivation treatment can also be bleached with alkali solution (white passivation). , but the corrosion resistance of the coating decreases.