CHROMATE-FREE CHEMICAL CONVERSION COATINGS ON ALUMINUM ALLOY 5556

Abstract

Recently, as an alternative to chromate protective layers at aluminum and its alloys, worldwide are used nanoscale adhesive coatings, obtained from hexafluorozirconic and hexafluorotitanic acids. The present study is devoted to the technology of development of these coatings. The process of deposition of titanium, zirconium-containing coatings at aluminum alloy 5556 is developed. In the process of performing the work, the basic patterns of coating formation were identified. The solution composition and process parameters were optimized, and the physicochemical properties were investigated. It is shown that passivation of aluminum alloy 5556 in a titanium,zirconium-containing solution increases its corrosion resistance to pitting corrosion. These coatings can replace chromate coatings because of good ability to resist corrosion. It was found that the thickness of titanium-, zirconium-containing coatings is about 100 nm.