Process for Black Trivalent Chromium Passivation of Galvanizing Coating Obtained in Potassium Chloride Solution

The optimal processing conditions for black trivalent chromium passivation of galvanizing coating obtained in KCl solution were established based on single-factor test and orthogonal test. The morphology of the passivation coating was observed using a scanning electron microscope. The effects of the composition of passivation fluid and technological parameters on the performance of the passivation coating were investigated. The corrosion resistance of as-prepared passivation coating was evaluated using dropping corrosion test of lead acetate and electrochemical test. It was found that black trivalent chromium passivation of the galvanizing coating plus follow-up sealing produced a uniform and bright black surface with significantly increased corrosion resistance.