A solution that dulls the surface of a metal. Generally used for zinc plating, cadmium plating and other coating after plating treatment. 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 the analysis of formula, it can be seen that the main components of commonly used passivating liquid are chromic acid, nitric acid and sulfuric acid. However, due to the environmental pollution caused by chromic acid, in some cases, the product requires silver or blue-white, the rainbow passivation film generated after the three acid passivation treatment can also be treated with lye bleaching (white passivation), but the corrosion resistance of the coating is reduced.
Electroplating additives according to the functional classification, electroplating additives can be divided into complexing agents, brighteners, surfactants, leveling agents, stress reliever, impurity removal agents and wetting agents, among which the most important is brighteners and surfactants. Function: to widen the range of pH, temperature and current density of electroplating solution; It has good dispersion of metal particles precipitated in electroplating, which is conducive to improving the smooth surface and brightness of plating parts. Reducing the surface tension is beneficial to the wetting of plated parts. Promoting the hydrogen generated on the cathode surface to be removed as soon as possible can prevent the plating from producing dents and pinholes; The plating effect of the plating parts cleaned by surfactants is obviously improved.
The main component of phosphating solution is dihydrogen phosphate salt, such as Zn(H2PO4)2 and an appropriate amount of free phosphoric acid and accelerator. Phosphating is a common pre-treatment technology, in principle should belong to the chemical conversion film treatment, mainly used in the surface of steel phosphating, non-ferrous metals (such as aluminum, zinc) can also be applied to phosphating. Phosphating is a chemical and electrochemical reaction to form a phosphate chemical conversion film process, the phosphate conversion film formed is called phosphating film. The main purpose of phosphating is to provide protection for the base metal and prevent the metal from being corroded to a certain extent; It is used for primer before painting to improve the adhesion and anti-corrosion ability of the paint film. It plays the role of anti-friction lubrication in the cold working process of metal.
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