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Trivalent hard chromium electroplating method

A technology of trivalent chromium and hard chromium, applied in the field of trivalent chromium hard chromium electroplating, can solve the problems of inability to plate thick chromium layer, low impurity tolerance, inability to produce qualified products, etc., and achieve the effect of white, bright and defect-free coating appearance

Inactive Publication Date: 2014-01-15
WUHAN RES INST OF MATERIALS PROTECTION +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, there are also some problems in trivalent chromium plating, mainly due to its low tolerance to impurities. For example, when the cumulative concentration of metal ions such as zinc, copper and nickel in the trivalent chromium plating bath reaches 10-100ppm, the chromium plating layer The quality will drop, resulting in poor stability and difficult to put into actual production application
The hexavalent chromium ions produced at the anode will also seriously affect the quality of the coating, so that qualified products cannot be produced at all.
Generally, the trivalent chromium plating solution sold in the market cannot plate a thick chromium layer, and there are relatively big problems in the stability and maintenance of the bath solution.
Trivalent chromium electroplating technology that can replace hexavalent chromium electroplating in various aspects has not been reported yet.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0023] Embodiment 1 solution preparation

[0024] Using potassium chromium sulfate 230g / L, buffering agent 120g / L, complexing agent 30g / L, catalyst 20g / L, conductive salt 50g / L, prepare the solution according to the following method.

[0025] First, put two-thirds of the deionized water into the container and heat it to above 60°C, put the main salt into the deionized water while stirring, then put in the complexing agent, catalyst and buffer in turn, and wait until all are dissolved , reserved for later use; . Put less than one-third of the measured deionized water into another container and heat it above 60°C. Put the buffer into the deionized water in this container while stirring. After it is completely dissolved, put it in the second container. Pour the solution into the first container, heat it to about 95°C, and keep it warm for more than 2 hours. When the temperature naturally cools down to the process temperature, use deionized water to make up the volume, and the pr...

Embodiment 2

[0026] Embodiment 2 Base material No. 45 steel shaft-shaped part (diameter 30*long 200mm)

[0027] Mechanical polishing——pre-chemical degreasing for 10 minutes—hanger, installation of shields—anode electrolytic degreasing for 5 minutes—secondary water washing—activation for 1 minute—secondary water washing—pure water washing—hard chrome plating (directly start to Specified current density) - secondary washing - pure water washing - unloading

[0028] The trivalent chromium plating is peeling off.

Embodiment 3

[0029] Embodiment 3 Substrate 65Mn steel shaft-shaped part (diameter 30*length 200mm, wherein the middle part of electroplating is 50mm long)

[0030] Mechanical polishing——pre-chemical degreasing for 10 minutes—hanger, installation of shields—anode electrolytic degreasing for 5 minutes—secondary water washing—activation for 1 minute—secondary water washing—pure water washing—hard chrome plating (mechanical stirring) ——Secondary water washing——Pure water washing——Unloading hanger

[0031] Plating cracked.

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Abstract

The present invention discloses an electroplating method for electroplating a trivalent hard chromium plating layer on iron and steel, wherein a DSA anode and a sulfuric acid system trivalent chromium solution are adopted, a temperature of about 50 DEG C and current density of 35-65 A / dm<2> are adopted, a soft starting process that change of current and a tank voltage is controlled during an electroplating process is adopted, and the pH value is maintained in the specified range (the pH value is 0.9-2.1) to obtain the trivalent chromium plating layer with a thickness of more than 80 mum, wherein the plating layer hardness achieves more than HV870, the current efficiency is more than 35%, the plating coating rate can be up to 2 mum / min, and the plating layer bonding force passes through the thermal shock test (200 DEG C heating, and salt water quenching). According to the present invention, the process method that the trivalent hard chromium electroplating replaces the sexvalent hard chromium electroplating with a characteristic of serious environment pollution is provided, and problems that the thick plating layer can not be obtained through the existing trivalent chromium electroplating technology, the plating layer and substrate bonding force is poor, and the like are solved.

Description

[0001] Technical field The present invention relates to the technology of electroplating hard chromium with trivalent chromium sulfate as main salt technical background [0002] Hexavalent chromium plating is one of the most widely used plating types in the electroplating industry. It has a large quantity and a wide range. Decorative chromium is plated on steel, aluminum, plastic, copper alloy and zinc-based alloy die castings. Functional electroplating (hard chrome) Plating workpieces include hydraulic cylinders and plungers, crankshafts, printing plates / rollers, internal combustion engine pistons, plastic molds, and fabrication of fiberglass workpieces, cutting tools, etc. Also used to repair worn workpieces such as rollers, molds, cylinders and crankshafts repair. Hexavalent chromium coating has good hardness, wear resistance, corrosion resistance and decorative properties. It is not only used for decorative coatings, but also widely used for functional coatings and repair ...

Claims

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Application Information

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IPC IPC(8): C25D3/06C25D3/10
Inventor 毛祖国李家柱丁运虎孙宁
Owner WUHAN RES INST OF MATERIALS PROTECTION
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