Research On Preparation And Performance Of A Novel Type Of Ti-Zr Conversion Coating Based On The Aluminum Alloy

Zirconium-titanium conversion coatings are most promising alternative to chromate conversion coatings at the present stage.and have been extensively studied domestically and abroad.However,when compared to those chromate conversion coatings which have been industrially applied,there lies a big gap in the corrosion resistance and adhesion between substrates and paint coatings,thus limits the industrial application of zirconium-titanium conversion coatings.In this paper,the optimal additive species of zirconium-titanium conversion coatings were evaluate by corrosion resistance test.According to the result,the coating formation processes were optimized..The conversion coatings manufactured with an aspartic acid addition amount of 3 g/L exhibit best corrosion resistance.The coatings forming and corrosion resistance mechanism of aspartic acid-zirconium titanium conversion coatings were determined by corrosion resistance analysis and corrosion morphology analysis.The addition of aspartic acid has complex reaction with Zr and Ti to form Zr-O bond and Ti-O,so that makes the conversion coatings denser,and also improves the corrosion resistance.Based on the asparagine zirconium titanium conversion coating processes,organic chitosan and polyvinyl alcohol(PVA)were added to manufacture new types of zirconium-titanium conversion coatings on the aluminum alloy.The corrosion resistance and adhesion between substrates and paint coatings has been significant improved.Electrochemical workstations,scanning electron microscopes,Fourier transform infrared spectrometers,and X-ray photoelectron spectrometers were used to evaluate the performance of the new conversion coatings.The results suggested that the coatings fabricated with the addition of 15ml/L chitosan show the best corrosion resistance.Chitosan can be co-deposite with zirconium and titanium,diffuse to the surface of the conversion coatings,and finally fill the gaps of the conversion coatings,As the results,the thickness of the coatings has been significantly improved,thus enhanced the corrosion resistance performance and adhesion.PVA contains many oxygen-containing groups.The lone pair of electrons on these oxygen-containing groups can combine with Zr and Ti ions,and then deposited on the surfaces of the substrates in the form of zirconium-titanium complexes.Therefore,enhanced the corrosion resistance of the coatings and combination to the substrates.In order to further investigate the performance and the combination strength of the conversion coatings after coated,the paint coatings were deposited on the surface of the conversion coatings.Drawing experiments,cross hatching experiments and salt spray experiments were used to judge the comprehensive properties of the new zirconium titanium conversion coatings.The results show that the addition of chitosan and polyvinyl alcohol polymer organics can significantly improve the adhesion between the zirconium titanium conversion coatings and the substrates or the paint coatings.It also inhibits the coatings' blistering and paint stripping phenomenon effectively during the salt spray experiments and long-term soaking processes...