Hard chrome machine plating process procedures

A, Plating processes introduction:

Hard chrome machine plating process procedures is a technology that coat a thick plating layer in a variety of matrix surfaces, its thickness generally more than 20μm , which making the use of chrome characteristic to improve parts performance of hardness, wear resistance , heat and corrosion resistance and other properties.

Hard chrome plating technological characteristics:

1)  Cathode current efficiency as high as 50 % to 65% , and the deposition rate very quickly;
2)  Coating layer hardness as (900 ~ 1200 HV), appear to homogeneously dense network cracks, has feature of good wear resistance;
3)  Electroplating solution dispersing ability good, coating thickness uniformity, and not easy to produce rough blister aneurysm phenomenon, which the plating layer appearance looks bright and green;
4)  The binding force between coating layer and the substrate is strong, and compare with traditional process, the pre-treatment similar and operating easier than the traditional process;
5)  Trivalent chromium content allowed tolerance in plating solution is wide, usually do not require discontinuation electrolysis to treatment trivalent chromium;
6)  Plating solution does not contain fluoride, excluding rare earth elements, and the workpiece without low zone corrosion.

Hard chromium has a very wide application, such as mechanical molds, cylinder piston, measuring, cutting and drawing tools. Its other usage is for repairing of worn parts and workpiece with excessive cutting, so that these parts can be reused.

B, Simple technical processes:

Inspection—degreasing—water washing rinse—antipole—chrome plating—water washing—testing.

C, Technological parameters:

1, Chromic anhydride:(CrO₃) 220 ~ 250g/L
2, Sulfate (SO₄^2-): 2.2 ~ 2.5g/L
3, Trivalent chromium (Cr³⁺): 2 ~ 5g/L
4, Plating solution temperature: 50 ~ 55℃
5, Cathode current density: 30 ~ 60A/dm²

D, Operations and precautions

1, Workpieces size inspection before plating, machining surface conditions, according to the coating thickness to calculate the plating time accurately.
2, Good controling of the electroplating solution working conditions, observation frequently, pay attention to temperature changes, level changes, careful operation, fill out the operating record. According to the result to add medicine, then correct plating solution.
3, Check the quality of the coating layer after plating, size, clean, wire teeth, inside bore and other parts rust protection. Steel workpiece strike operating grade of steel, deburring edges.
4, If the acid spilled on the skin, should immediately rinse and clean with water.