In the passivation treatment process of aluminum alloy surface, countless researchers have done in-depth research. At present, the passivation treatment method of chromate is widely used in the market. The passivation effect of this kind of heavy metal passivation process is acceptable, but it has serious environmental pollution, especially the passivation method such as the use of hexavalent chromium passivation agent, which is also very toxic. In view of this situation, research on chromium-free passivation has also been carried out. Now there are chromium-free passivators that have been put into production. Then, how to achieve the environmental protection of aluminum alloy and other metals without chromium passivation?

Here we introduce some molybdate and tungstate passivation treatment methods for other metals.

Molybdate passivation. Molybdenum belongs to the same group as chromium, and molybdate has been widely used as corrosion inhibitor and passivator for steel and nonferrous metals. The methods of molybdate passivation treatment mainly include anodic polarization treatment and chemical immersion treatment. Studies have shown that the effect of molybdate passivation is not as good as that of chromate passivation, but it can significantly improve the corrosion resistance of metals such as zinc and tin.

Tungstate passivation. Tungsten is in the same family as Cr and Mo, and tungstate is similar to molybdate as a metal corrosion inhibitor, so tungstate passivation has also been studied. D.Bijimi et al. have studied the characteristics of cathodic and anode polarization of some metals in tungstate. The 24h salt spray test shows that in the passive film formed on the surface of zinc, the corrosion resistance of tungstate passive film is inferior to that of chromate. passivation film. According to the experimental results, the salt spray resistance and damp heat cycle test performance of the tungstate passivation film are worse than those of the molybdate and chromate passivation films.

Here is another look at passivation methods using trivalent chromium. The toxicity of trivalent chromium is only about 1% of that of hexavalent chromium, so its research has certain significance. Trivalent chromium can obtain passive films of different colors by using different additives. In the application of aluminum alloy surface passivation, trivalent chromium is widely used, its toxicity is small, and the pollution to the environment is much lower than that of hexavalent chromium, and the passivation effect can also meet the production requirements-generally use ht433 three Chromium-valent passivator can obtain excellent anti-corrosion and anti-rust film layer, and the cost is low, and the service life is also very long, but there are also some manufacturers who directly use ht407 chromium-free passivator on the market.