Preparation And Characterization Of Corrosion Resistant Performance For Composite Passivation Film Containing Ti&Zr Oxides-silane On The Aluminum Sheet

This paper has mainly investigated the influence factors and their effect degreeson the KH560silane coupling agent (SCA) hydrolysis system. The orthogonalexperiment method has been employed to identify the best formula and hydrolysisconditions of KH560hydrolysis solution as soon as its passivation process conditions.In addition, the components constituting and passivation conditions of Ti-Zr oxidespassivation solution has also been optimized. The two-step passivation approach hasbeen adopted for preparation of composite passivation film containing Ti&Zr oxidesand SCA. The corrosion resisting properties of as prepared passivation film for Alsheet have been characterized using the methods as follows, the copper sulfatedripping accelerated corrosion, the boiling in water, and the electrochemical testing.The metallographic microscope has been used to observe the surface morphology ofas prepared passivation film.In the KH560hydrolysis system, the influencing degrees from the most to theleast was in the order of the KH560concentration, temperature, pH value, glycerolcontent, and methanol content. The optimum formula of SCA hydrolysis system wasthat the KH560volume content being15%, glycerol mass concentration being2g/L,and the methanol volume content being10%. The optimum hydrolysis conditions forKH560were that the temperature being35℃and pH value being4. The optimumpassivation process conditions for KH560passivation solution were that thepassivation temperature being40℃, passivation time being40s, curing temperaturebeing100℃, and curing time being60min.For Ti&Zr passivation solution, the optimum formula was that the massconcentrations of [ZrF6]2-,[TiF6]2-, and nitric acid being0.24g/L,0.48g/L, and0.6g/L respectively. At the same time, the optimum passivation conditions were that thepH value being3.5, the passivation time being120s, and the passivation temperaturebeing50℃. In the preparation of Ti&Zr oxides-Silane composite passivation film, it wasfound that the composite passivation solution was become into unstable with timeexpanding as the Ti-Zr passivation solution and KH560hydrolysis solution mixingtogether whatever the former added into the latter or the opposite.The Ti&Zr oxides-SCA composite passivation film with ideal corrosion resistingproperty can be prepared using two-step passivation approach, and the as preparedcomposite passivation film has made up the deficiency of Ti-Zr oxides passivationfilm. As compared with the SCA passivation film and the Ti-Zr oxides passivationfilm, the as prepared composite passivation film has a greater degree of improvementon the corrosion resistance tested with various method. Metallographic analysis hasshown that the Ti&Zr-SCA composite passivation film had a dense and homogeneousstructure, and it was a kind of hybrid film composed of silane, zirconium oxide andtitanium oxide particles.