Trivalent chromium coating and preparation method thereof

Abstract

The invention relates to the field of trivalent chromium electroplating, in particular to a trivalent chromium coating and a preparation method thereof. The preparation method of the trivalent chromium coating at least comprises the following steps that a substrate is dipped in a trivalent chromium electroplating bath, electroplating is conducted with the substrate as the cathode, the electroplating temperature is 20-45 DEG C, the current density is 6 A/dm<2> to 25 A/dm<2>, and the electroplating time is 5-30 min; the substrate is coated with the trivalent chromium coating in a plated mode; the surface of the substrate at least comprises a conducting layer; and the trivalent chromium electroplating bath at least comprises the following components of, by weight, 15-20 parts of water-soluble chromic salt, 12-16 parts of cobalt salt, 20-35 parts of conducting salt, 4-6 parts of a coordination agent, 7-10 parts of a buffering agent, 0.5-1.6 parts of a blackening agent, 0.01-0.5 part of a brightener and 100 parts of deionized water.

Description

technical field [0001] The invention relates to the field of trivalent chromium electroplating, in particular to a trivalent chromium coating and a preparation method thereof. Background technique [0002] Black chrome coating is a special coating among functional chrome coatings. Because of its good physical and chemical properties, solemn and magnificent appearance, and good wear resistance, corrosion resistance and temperature resistance, it is widely used. The main components of the black chromium coating are metal chromium and chromium oxide. The chromium oxide particles are dispersed in the metal chromium medium. Due to the interband transition of metal chromium and the resonance of the chromium oxide particles, the black chromium coating has a strong absorption effect on solar radiation. Black chrome plating is often used on parts such as cameras, optical instruments, military weapons, and instrumentation systems to prevent diffuse reflection of light; in order to ach...

AI Technical Summary

Problems solved by technology

At present, a lot of work has been done on the research of trivalent chromium plating solution at home and abroad. Among them, the replacement of hexavalent chromium plating solution with trivalent chromium plating solution has been gradually popularized and applied in decorative chrome plating, but the research on trivalent chromium electroplating black chromium is relatively limited. less, and basically all of them are chloride systems, which have poor impurity resistance, serious corrosion of the plating tank caused by chlorine gas at the anode, and difficult maintenance of the plating solution. Moreover, the current black chromium coating still has a dark surface and poor brightness , high porosity of the coating, poor corrosion resistance and poor bonding between the coating and the substrate, etc.

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