Trivalent Chromium Passivation Process for Zinc Coating

Zinc coatings were passivated under different pH value,temperature and processing time by using a modified trivalent chromium solution with the addition of oxidant and chelating agent.The effect of processing parameters on the corrosion resistance of passivated zinc coating was determined in 50g/L NaCl solution soaking test.The results show that the corrosion resistance of zinc coating was improved obviously after the modified trivalent chromium solution passivation.There was no white rust on the coating after 168 hours soaking test,which is equivalent with the coating passivated by hexavalent chromium solution.