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Trivalent chromium passivation technology

  • Author:Jack Zou
  • Source:www.diecastingpartsupplier.com
  • Release on:2014-11-18

Our many products need this surface treatment,for example,Decoration aluminum top cover accessories,High quality aluminum base for equipment,Die casting ADC12 component parts,OEM/ODM Casting Aluminium Die Casting plate.

The adjustment of the p H
In the laboratory, largely determine the color trivalent chromium passivation technology formula: chromium nitrate, 20 ~ 30 g/L; Antioxidant, 4 ~ 5 ml/L; PH adjusting agent, 4 ~ 6 ml/L; PH 1.5 ~ 2.0. According to the trivalent chromium passivation technology to determine the pH range, pH below 1.0 passivation membrane layer of mist, rapid reaction, when pH above 2.5 passivation film layer of colour and lustre is uneven.

Given the nature of the parts, test of trivalent chromium passivation formula one is: chromium nitrate, 20 ~ 30 g/L; Antioxidant, 3 ~ 8 ml/L; PH adjusting agent, 4 ~ 6 ml/L; PH 1.5 ~ 2.0; T, 30 s ~ 1 min. Theta, 35 ~ 45 ℃. The trivalent chromium passivation technology color bright color, uniform colour passivation membrane, the wide range of operating conditions, suitable for mass production, automation.

The adjustment of the oxidant
According to the formula of oxidant concentration in the range of 3 ~ 8 ml/L, oxidant concentration low passivation film is used fog, oxidant concentration is high quality passivation membrane layer of colour and lustre is gorgeous, but easy to take off the membrane.

Given the nature of the parts, test of trivalent chromium passivation formula one is: chromium nitrate, 20 ~ 30 g/L; Antioxidant, 3 ~ 8 ml/L; PH adjusting agent, 4 ~ 6 ml/L; PH 1.5 ~ 2.0; T, 30 s ~ 1 min. Theta, 35 ~ 45 ℃. The trivalent chromium passivation technology color bright color, uniform colour passivation membrane, the wide range of operating conditions, suitable for mass production, automation. Different parts of blocking agent Trivalent chromium passivation film of no leak of hexavalent chromium, so there was no film self-healing capability, is easy to happen when the passivation membrane caustic corrosion. In order to make up for the defect, can adopt closed treatment.

According to the different parts in different using conditions, and its corrosion resistant performance is not consistent, therefore need to carry on the adjustment of blocking agent. Adopted by the blocking agent mass fraction from 4% ~ 20%, and in order to meet the parts corrosion resistance and heat resistance. Casting and acid zinc trivalent chromium passivation colour The alkaline zinc coating technology of trivalent chromium passivation color used in casting pipe.