Alumina sol-gel film for pretreatment to paint on aluminum alloy

摘要

Aluminum alloy coatings for pretreatment are developed by sol-gel method. The adhesion between sol-gel film and the paint film was measured by scratching circles and corrosion resistance of sol-gel film was tested by salt spraying experiment. The adhesion between sol-gel film made by pure alumina sol and the paint film was so poor that it is unsuitable for ground coatings, but the composite sol which ultrafine Al_2O_3 powder was added to pure alumina sol can improve the adhesion and corrosion resistance. If the first layer film is made of pure alumina sol and the second layer is made of composite sol, the neutral salt spraying time of double layers film is longer than the single-layer composite sol-gel film. The adhesion for both double composite film and single-layer composite sol-gel film are first-grade. When solution of potessium dichromate is dropped on double combinatorial film for 100s, the solution will change in color. The gloss of paint film on double composite sol-gel film is 0.827, flexibility is 2X10mm and impact resistance is lkg-50cm. It is possible that composite sol-gel film or combinatorial sol-gel film replace dichromate salt conversion film on aluminum alloy using for painting pretreatment.