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A method for converting existing hexavalent chromium plating solution into new trivalent chromium plating solution

A technology of trivalent chromium and hexavalent chromium, which is applied in the field of converting existing hexavalent chromium plating solution into new trivalent chromium plating solution and electroplating chromium, and can solve the problems of slow solution plating speed, poor corrosion resistance and large consumption of chemical materials and other problems, to achieve the effects of decreased kinetic stability, accelerated electrodeposition speed, and environmental protection.

Active Publication Date: 2017-11-14
WUHAN RES INST OF MATERIALS PROTECTION
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] Compared with hexavalent chromium, the trivalent chromium plating solution obtained by these methods has lower toxicity and relatively easy waste water treatment; but there are two major defects: one is because the used trivalent chromium salt contains a large amount of anions, resulting in The concentration of trivalent chromium ions can only reach 20-30g / L, and higher concentrations cannot be configured. The solution plating speed is slow, there are many inclusions, and the corrosion resistance is poor; The hexavalent chromium plating solution is either solved by wastewater treatment, which consumes a large amount of chemical materials and forms a large amount of chromium-containing waste residue, or is sealed on the spot, forming a serious environmental hazard

Method used

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  • A method for converting existing hexavalent chromium plating solution into new trivalent chromium plating solution

Examples

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Effect test

Embodiment 1

[0016] (1) Existing hexavalent chromium plating solution, its hexavalent chromium content is 250g / L, dilute the plating solution with pure water to hexavalent chromium 140g / L, take 100L plating solution and use 20% sulfuric acid to adjust the pH of the bath value to 0.5, heat to 80-90°C, under stirring, according to the molar ratio of reducing agent and hexavalent chromium is 3:1, slowly and gradually add reducing agent methanol 13.4kg and complexing agent citric acid 57.6kg until the reaction is completed , maintain the temperature at 90°C and keep it warm for 4 hours to form an active ligand [Cr(H 2 C 6 h 6 o 7 )(H 2 O) 5 ], this existing hexavalent chromium plating solution is then converted into a trivalent chromium active ligand basic solution with a trivalent chromium content of 75g / L;

[0017] (2) In the trivalent chromium active ligand basic solution formed by the above-mentioned reaction, add conductive salt ammonium sulfate 5kg, potassium sulfate 5kg and catalys...

Embodiment 2

[0019] (1) Existing hexavalent chromium plating solution, its hexavalent chromium content is 250g / L, dilute the plating solution to 140g / L with purified water, get 100L plating solution and adjust the pH value of bath solution to 0.5 with 20% sulfuric acid, Heat to 80-90°C, under stirring, according to the molar ratio of reducing agent to hexavalent chromium is 3:1, slowly and gradually add reducing agent ethanol 19.7kg instead of methanol, add complexing agent citric acid 57.6kg, until the reaction is completed, Maintaining the temperature at 90°C for 4 hours, the existing hexavalent chromium plating solution is converted into a trivalent chromium active ligand basic solution with a trivalent chromium content of 75g / L;

[0020] (2) In the trivalent chromium active ligand basic solution formed by the above-mentioned reaction, add conductive salt ammonium sulfate 5kg, potassium sulfate 5kg and catalyst, sodium methanedisulfonate 200g, stir until all dissolve, adjust and form tri...

Embodiment 3

[0022] (1) Existing hexavalent chromium plating solution, its hexavalent chromium content is 250g / L, dilute the plating solution to 140g / L with purified water, get 100L plating solution and adjust the pH value of bath solution to 0.5 with 20% sulfuric acid, Heat to 80-90°C, under stirring, according to the molar ratio of reducing agent and hexavalent chromium is 3:1, gradually add reducing agent methanol 13.4kg, use 18.9kg of oxalic acid and 21.8kg of malonic acid to replace the example 1, until the reaction is complete, maintain the temperature at 90°C, and keep it warm for 4 hours to form an active ligand [Cr(C 2 o 4 h 2 )(C 3 o 4 h 2 )(H 2 O) 4 ], this existing hexavalent chromium plating solution is then converted into a trivalent chromium active ligand basic solution with a trivalent chromium content of 75g / L;

[0023](2) In the trivalent chromium active ligand basic solution formed by the above reaction, add conductive salt ammonium sulfate 5kg, potassium sulfate ...

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Abstract

The invention discloses a method for transforming an existing hexavalent chromium plating solution into a new trivalent chromium plating solution and belongs to the technical field of electroplating. The method comprises the two steps that firstly, under the conditions that the pH value of the existing hexavalent chromium plating solution is 0.5-1.0 and the temperature is 80-90 DEG C, a specified amount of a reducing agent and a specified amount of the organic acid complexing agent are added, and heat preservation is conducted for two to four hours, so that hexavalent chromium is reduced to trivalent chromium and the trivalent chromium and an organic acid complexing agent form a trivalent chromium active ligand basic solution with the ligand structure being [CrLx.(H2O)6-x]; and secondly, the trivalent chromium active ligand basic solution is adjusted to become the new trivalent chromium plating solution by adding conducting salts and a catalyzer into the trivalent chromium active ligand basic solution formed in the first step. According to the method, the existing hexavalent chromium plating solution is effectively transformed into the environmental-friendly trivalent chromium plating solution, and the new trivalent chromium plating solution is high in electroplating speed under the standard condition; a chromium plated coating is good in brightness and uniformity, high in hardness and excellent in corrosion property, so that the chromium plated coating can be on a par with a chromium plated coating of the hexavalent chromium plating solution.

Description

technical field [0001] The invention discloses a method for converting an existing hexavalent chromium plating solution into a nascent trivalent chromium plating solution, belongs to the technical field of electroplating, and specifically relates to the electrochromium plating technology. technical background [0002] Chromium plating is widely used in hardware, electromechanical, automobile and other industries because of its bright, hard, anti-discoloration, excellent wear-resistant and corrosion-resistant properties. For a long time, the chromium plating process is a hexavalent chromium electroplating process using chromic acid as the chromium source. Hexavalent chromium is one of the most serious and difficult pollution sources in the electroplating process. The U.S. Environmental Protection Agency (EPA) identified hexavalent chromium as one of 17 highly dangerous toxic substances. Chromium exists in trivalent and hexavalent forms in water, and hexavalent chromium is ve...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C25D3/06C25D3/10
CPCC25D3/06C25D3/10
Inventor 丁运虎黄兴林毛祖国邓华才肖伟平王柱元
Owner WUHAN RES INST OF MATERIALS PROTECTION
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