What is hexavalent chromium-free passivation of galvanized sheet?

1. The passivation of hexavalent chromium is because the reduction reaction of hexavalent chromium forms a self-healing function on the galvanized surface, which ensures the oxidation resistance of galvanized sheet, but it is easy to produce yellow spots. Passivation of trivalent chromium mixed with hexavalent chromium effectively reduced the appearance of yellow spots on the coating.

2. The toxicity of hexavalent chromium is a fatal defect. With the improvement of environmental protection requirements, it is necessary to use non-toxic passivator to replace hexavalent chromium passivation, so various non-hexavalent chromium passivation technologies have emerged: first, trivalent chromium passivation is used to replace toxic hexavalent chromium passivation; Secondly, chromium-free passivation is used to replace trivalent chromium and hexavalent chromium passivation. Chromium-free passivation technology is an organic-inorganic composite silane modified material, which can give consideration to the performance and environmental protection requirements of the plate.

3. There are 9 kinds of research systems to replace hexavalent chromium passivation at home and abroad, among which the organic-inorganic composite technology based on silane materials is an international research hotspot, accounting for 70% of such patents. Therefore, the organic-inorganic composite technology based on silane materials is an international research hotspot.