Study On Self-healing Characteristics And Mechanism Of Colored Ti-Zr-V Conversion Film On 6063 Aluminum Alloy Surface

Aluminum alloy is widely used in aerospace,architectural profiles due to its excellent performance.However,the potential of aluminum is negative,and various types of corrosion are likely to occur.In industrial applications,surface protection of aluminum alloys is required.Chromate conversion coating with excellent corrosion resistance and self-healing property has been banned because of containing toxic and carcinogenic hexavalent chromium.Chromium-free conversion technology has attracted much attention,recently.According to previous research,the colored Ti-Zr-V conversion coating prepared by adding NaVO₃ has excellent corrosion resistance and self-healing property equivalent to chromate conversion coating,but the self-healing process and its dominant factors are still unclear.Therefore,this study explores the effect of components on self-healing through component adjustment and discusses the role of NaVO₃.Also,the self-healing process of Ti-Zr-V conversion film is observed.Puts forward the self-healing mechanism.Through composition adjustment,it was found that tannic acid mainly played an important role in coloring and improving the corrosion resistance of the layer,while NaVO₃ was used as oxidant to accelerate the film formation process.The film compounded with NaVO₃ has self-healing property,while consisted of TA has not exhibit self-healing property.The research on the self-healing of NaVO₃ film showed that the artificial scratch gradually healed and the corrosion resistance gradually recovered with the extension of treated time,and the NaVO₃ film had self-healing property.Soluble V₂O₅ in the film plays the vital role in self-healing process,while V₂O₃,VO₂ and Al₂O₃ play the role of forming insoluble skeleton and adsorb V₂O₅.Soluble V₂O₅ dissolves and diffuses to scratch,and reacts to form vanadium suboxide.Composite conversion film with self-healing property was gained by adding NaVO₃ to TA.The film constitutes of insoluble V₂O₃,VO₂,Al₂O₃,Al and V organic complexation,and V₂O₅.As time went on,the defects gradually restored and the corrosion resistance of the film improved.Self-healing ability of the film was caused by the dissolution and diffusion of V₂O₅which is adsorbed in the layer to the scratch,and then happened the oxidation-reduction reaction to produce the vanadium suboxide.Self-healing property of Ti-Zr-V composite film was studied.The film has similar self-healing property to chromate conversion coating.And moreover,the film was made up by organic complexes such as Al,Zr and Ti complexion,as well as oxides and fluorides,among which organic complexes account for a large proportion.After self-healing,a new film developed at the bottom of the scratch,and the self-healing process was related to the dissolution,hydrolysis and diffusion of V₂O₅.The material composition at the scratch after self-healing was mainly vanadium suboxide.In conclusion,the self-healing property and self-healing mechanism of Ti-Zr-V conversion coating were systematically explored in present study.The study can provide important reference value and theoretical guiding significance on the subsequent research and development of functional conversion coating from the perspective of composition design.