| The hard anodization is a common surface treatment method for aluminum and its alloys.The surface of AAO?anodic aluminum oxide?film has many micropores and is easy to adsorb corrosive medium,causing damage to the structure and properties of aluminum and its alloys.Therefore,it is necessary to seal the porous AAO film.Traditional sealing methods such as dichromate sealing and nickel salt sealing,can produce great harm to the environment and human body and its application is strictly restricted in many ways.It is more and more urgent to seek a green and effective sealing method.?1?Organic acid 1 and 2 was used as the electrolyte,AAO film with thickness of about 30?m was prepared on 3003 aluminum alloy.Then,the effects of zirconium salt sealing process parameters on the corrosion resistance of AAO film were studied through strong alkali immersion experiment,film thickness sloss and Tafel curve analysis,and the optimum conditions of zirconium salt sealing were obtained:K2ZrF61.5 g/L,NaF 0.3 g/L,25?for 8 min.The results showed that the bubble time of zirconium salt sealing film was 8 min in strong alkali,and its corrosion current density was 1.493?A/cm2.However,the bubble time of unsealing film was 2 min in strong alkali,and its corrosion current density was 3.116?A/cm2.Compared with the unsealing AAO film,the bubble time of zirconium salt sealing film increased and its corrosion current density decreased greatly.The order of corrosion resistance of oxide film was:nickel salt sealing>zirconium salt sealing>boiling water sealing>unsealing.The microstructure and surface elements of zirconium salt sealing oxide film were analyzed by SEM and EDS.The results showed that a dense film formed on the surface of porous AAO film after zirconium salt sealing,and the sealing film had a good sealing effect.The zirconium salt sealing film was composed of C,O,F,Al,Zr and S elements.?2?Organic acid 1 and 2 was used as electrolyte to obtain AAO,and effects of sealing process parameters on the corrosion resistance of organosilane sealing film was studied.The optimum conditions of organosilane sealing was obtained:Firstly,hydroxylation of AAO film was carried out at 70?water bath for 15 min.Then,the hydroxylated specimens were immersed in the organosilane sealing solution at 30?for 10 min.Finally,the sealing film was treated at 200?for 30 min in the muffle furnace.The treatment process with the sealing liquid of organosilane was V total=200mL,V ethanol:V water=2:1,the volume of organosilane 50 mL,hydrolysis time was 24h.The results showed that the bubble time of organosilane sealing film was 11 min in strong alkali,and its corrosion current density was 0.381?A/cm2.The corrosion resistance of organosilane sealing film was better than unsealing AAO film.The order of corrosion resistance of oxide film swas:organosilane sealing>nickel salt sealing>boiling water sealing>unsealing.The surface of AAO film sealed by organosilane had a flat layer from surface morphology analysis,and the layer of sealing film can effectively block the corrosion ion entering the AAO film micropores.The organosilane sealing film was composed of C,O,Al,S and Si elements.?3?Zirconium salt sealing+silicate sealing,zirconium salt sealing+organosilane sealing,silicate sealing+organosilane sealing,zirconium salt sealing+silicate sealing+organosilane sealing were carried out.The results showed that the composite sealing of“zirconium salt sealing+silicate sealing+organosilane sealing”could form inorganic-inorganic-organic composite sealing film on the surface of AAO film,and the sealing film had the best corrosion resistance.The bubble time of“zirconium salt sealing+silicate sealing+organosilane sealing”sealing film was 21 min in strong alkali,and its corrosion current density was 0.062?A/cm2.The corrosion resistance was much better than those of unsealing and traditional sealing films.The surface of AAO film sealed by“zirconium salt sealing+silicate sealing+organosilane sealing”had a very dense and smooth layer from morphology analysis,and it had good hydrophobicity.The composite sealing film of zirconium salt sealing+silicate sealing+organosilane sealing was composed of C,O,F,Al,Si,Zr and S elements. |
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