A Study On Aluminum Phosphating

The aluminium material depends on its own excellent performance to be used widely in lots of fields, especially in the automobile, household appliances and building materials fields. In order to match with cathode electrophoresis coating better, strengthen coating adhesion and corrosion resistance, in the pretreatment of aluminium material paint, it generally uses chromium phosphating and passivation. The aluminium chromate-free phosphating has been used abroad, but it is used lessly in domestic and the relevant research is carried out little. There is an important economic benefit and social benefit to carry out the aluminium chromate-free phosphating.The performance of accelerator, fluoride, Mn²⁺, Ni²⁺, Zn²⁺, PO₄ and Fe²⁺ are studied by adopting SEM, XRD, potential vs. time change, film weight vs. time change. Studies have shown: gudnideue nitrate is a good kind of accelerator which has characteristics of good water dissolution and low consumption; the fluoride can promote forming phosphate film, increase the film weight and thin crystalline grain; Mn²⁺, Ni²⁺can make the crystallization thin obviously, make the film more uniform and compact, improve the film appearance; when the content of Zn²⁺ is low, the film can't be formed or the film is very bad, with the increase of Zn²⁺content, film weight increases too; PO₄ content has an important effect on film weight, the increase of PO₄ content can increase film weight.Research and solve the technology of aluminum phosphating in forming "P ratio", studies have shown: Fe²⁺ has an unique effect on forming "P ratio", an amount of Fe²⁺ can make aluminum sheet form phosphate film with "P ratio" like the steel phosphating. The study on cathode electrophoresis coating adhesion and corrosion resistance indicate, the performance of phosphate film-paint film double-layer with high "P ratio" is better than that of with low "P ratio" in neutral salt spray test.ALX phosphating composition, the process and the parameters are studied by orthogonal experiment. ALX performance test indicates that ALX has the characteristics of compact granular crystallization and light film weight and high "P ratio". The adhesion of ALX is as good as that of chromate treatment, is better than that of phosphating abroad and domestic. In...