| Because of its low density,high specific strength,high conductivity and good thermal conductivity,aluminum alloy is widely used in the field of ship and marine equipment.However,the corrosion of aluminum alloy is very serious in the harsh environment of sea and seawater.At the same time,the marine environment,hull fouling problem is also very prominent that caused by the adhesion of microorganisms and other marine pollutants.Therefore,the marine aluminum alloy should take into consider both the corrosion and anti fouling problem.In recent years,TiO2 thin film has good chemical stability,excellent photocatalytic performance and has great potential in application of antibacterial and self cleaning,surface anti fog and metal protection.In this paper,TiO2 thin films were prepared by sol-gel method on the surface of aluminum alloy,the corrosion resistance of the films was analyzed.Then,the composite films were prepared by micro arc oxidation pretreatment and sol-gel process.The corrosion resistance and anti-fouling properties of the prepared films were studied.The main contents include:(1)TiO2 thin films were prepared by sol-gel method,and the proportion of the sol was studied.When the deionized water was 4ml,the amount of polyethylene glycol 2000 was 1.6g,the surface of TiO2 film was smooth,no crack and other defects.When the heat treatment temperature is 500?,the content of anatase is higher.(2)Through the design of orthogonal experiment,the technological parameters of micro arc oxidation pretreatment of aluminum alloy were optimized.The optimal process parameters for the pretreatment of micro arc oxidation are current density 15A/dm2,TiO2 concentration 4g/L.TiO2 composite films prepared by sol-gel method on the surface of micro arc oxidation.The surface morphology and phase composition of the films were analyzed by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD).(3)Electrochemical impedance spectroscopy(EIS)was used to study the corrosion mechanism of sol-gel and composite thin films in seawater.The polarization curves show that the self corrosion potential of the composite films is positive and the self etching current density decreases compared with matrix and sol-gel film,which indicates that the corrosion resistance of the composite films is better.After 1000h of artificial seawater immersion and 500h salt spray test,the surface corrosion of the substrate and sol-gel film was more serious,and the composite film was not changed after the test compared with the start.With the prolonging of the micro arc oxidation pretreatment time,the corrosion resistance was increased.(4)By measuring the contact angle of the film surface,it is concluded that with the increase of heat treatment temperature,the film gradually changes from hydrophilic state to hydrophobic state.After heat treatment at 500?,the contact angle of the film surface is 134.4°,which is close to that of the super hydrophobic state.The contact angle of the composite films increases with the pretreatment time,but it is always hydrophilic state.The photocatalytic activity of thin films were characterized by the degradation of methylene blue.The photocatalytic effect of sol-gel thin film is very small,the photocatalytic effect of composite films are obvious,and the photocatalytic degradation rate is 51.1%of 20min micro arc oxidation pretreatment.By observing the growth of E.coli on the surface of the samples,the antimicrobial properties of films were characterized.The thin film surface of sol-gel is less,mainly due to electrolytic polished surface that is not easy to be attached to the microorganism.In the composite thin films,the adhesion of the films that micro arc oxidation pretreatment 20min was less than others,which confirmed that the content of TiO2 was more,and the photocatalytic performance was better. |
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