What is Passivation For Zinc Alloyed Steels
What is Passivation For Zinc Alloyed Steels
Zinc alloy steel passivator is mainly used to improve the corrosion resistance of zinc alloy steel. In the traditional passivation treatment, chromate passivation is a common method, which forms a protective film on the surface of zinc alloy to improve its corrosion resistance and decoration. However, chromate contains hexavalent chromium, which is harmful to human body and the environment, so chromium-free passivation technology has gradually become a research hotspot.
Chromium-free passivation techniques include inorganic passivation and organic passivation. Inorganic passivation mainly includes molybdate passivation, tungstate passivation, silicate passivation, rare earth metal salt passivation, etc. Organic passivation includes phytic acid passivation, tannic acid passivation, diaminotriazene (BAT4) and its derivatives passivation, and acrylic resin passivation processes. Among them, molybdate passivation process is the main research direction of chromium-free passivation.
In practical application, a chromium-free blue-white passivation process adopts inorganic salt organic acid cooperative passivation technology, uses sodium molybdate and sodium phosphate as the main salt of passivation solution, and is mixed with organic acid, can form blue-white passivation film on galvanized steel plate, its corrosion resistance and chromate passivation film is comparable, is expected to replace the traditional chromate passivation.
In addition, the passivation treatment of zinc alloy materials also includes the surface passivation of products such as electric galvanized layer, hot dip galvanized layer and zinc alloy castings to prevent zinc from contacting with external corrosive media, reduce the generation of white rust, and improve the decorative performance and corrosion resistance of products.
Environmentally friendly passivating agents, such as trivalent chromium passivating agents, are gradually being widely used because they do not contain hexavalent chromium, lead, cadmium, mercury and other harmful elements. These products are not only environmentally friendly, but also form a uniform, bright and corrosion resistant film on the surface of zinc alloy, which is suitable for the surface passivation and coating treatment of aluminum castings, copper and aluminum alloys.
Electrogalvanizing, which is widely used in automobile, building materials, household appliances and other fields, also needs passivation treatment in order to improve its corrosion resistance. With the improvement of environmental protection requirements, the development of environmentally friendly, chromium-free passivating agents is the trend of industry development.
