Trivalent chromium electroplating solution of sulfate system and electroplating method thereof

Abstract

The invention provides a trivalent chromium electroplating solution of a sulfate system. The trivalent chromium electroplating solution is characterized by comprising the following components in molarconcentration (mol / L): chromium sulfate0.2-0.6, potassium sulfate 0.5-1.5, ammonium bromide 0.02-0.5, boric acid 0.5-1.2, sodium hypophosphite 0.1-1, ferrous sulfate 0.01-0.1, complexing agent 0.2-2.0, thickening agent 0.01-0.5 and the balance of water. The invention also discloses an electroplating method for the electroplating solution. Compared with the prior art, the electroplating solution and the electroplating method have the advantages that: the electroplating solution is clean and pollution free, the thickness of the plating layer reaches 20 to 80mu m, the plating layer is smooth with few cracks and high bonding force, the source of raw materials is rich, the cost is lower, the performance-to-price ratio is good, the electroplating solution can be continuously used for electroplating for 0.5 to 5 hours, the hardness of the plating layer is 600 to 700HV, and after thermal treatment, the hardness of the plating layer can reach 1,200HV.

Description

technical field [0001] The invention relates to a trivalent chromium electroplating solution of a sulfate system, and also relates to an electroplating method of the electroplating solution. Background technique [0002] The existing chromium plating layer has high hardness, good wear resistance, corrosion resistance and decorative properties, and is one of the most widely used plating types in the electroplating industry. The current traditional hexavalent chromium plating technology is still widely used, and there are many defects, such as poor dispersion and coverage, low current efficiency, high plating temperature, the most important problem is that the hexavalent chromium plating process has high toxicity, heavy pollution, and waste water. It is difficult to deal with and seriously pollutes our country's water, soil and atmospheric environment. Several major countries in the world have successively promulgated laws to restrict or prohibit electroplating processes relat...

AI Technical Summary

Problems solved by technology

The current traditional hexavalent chromium plating technology is still widely used, and there are many defects, such as poor dispersion and coverage, low current efficiency, high plating temperature, the most important problem is that the hexavalent chromium plating process has high toxicity, heavy pollution, and waste water. It is difficult to deal with and seriously pollutes our country's water, soil and atmospheric environment. Several major countries in the world have successively promulgated laws to restrict or prohibit electroplating processes related to hexavalent chromium. For example, the European Parliament and the Council issued the RoHS directive on January 23, 2003. Europe will completely prohibit the circulation of electronic and electrical equipment containing hexavalent chromium in the European market on July 1, 2006; the U.S. Environmental Protection Agency will completely ban the hexavalent chromium electroplating process before 2010; "Regulates to control the use of hexavalent chromium from March 2007

[0003] At present, the technology to replace hexavalent chromium electroplating mainly includes electrodeposition alloy coating and trivalent chromium electroplating. Among them, trivalent chromium electroplating has low toxicity, only one percent of hexavalent chromium, low energy consumption, good dispersion ability and covering performance. Therefore, people have done a lot of research on trivalent chromium plating, but at present it can only be used for decorative plating, not for hard chromium plating

Trivalent chromium electroplating solutions mainly include chlorate system, chloride-sulfate system and sulfate system, etc. The anode of the chlorate system electroplating process is mainly based on chlorine evolution reaction, and the precipitated chlorine gas not only corrodes equipment, but also seriously pollutes the environment. For example, the Chinese invention patent "A Trivalent Chromium Electroplating Solution" (authorized announcement number: CN1042753C) whose patent number is ZL94105903.0, the plating solution in this patent consists of 0.3-0.4mol / L CrCl 3 ·6H 2 O, 0.6~0.8mol / L HCOOH or HCOONH 4 , 0.1~0.2mol / L NaBr, 0.8~1.0mol / L NaCl or KCl, 2.0~2.5mol / L NH 4 Cl, 0.6~0.8mol / L H 3 BO 3 And the appropriate amount of surfactant and rare earth additives, the plating solution will inevitably produce a large amount of chlorine gas and pollute the environment during the electroplating process. At the same time, there are still shortcomings such as unstable plating solution, dark coating color, slow crystallization speed, and low current efficiency.

[0006] One of the main problems in the current trivalent chromium plating is that the coating cannot be continuously thickened