Preparation And Corrosion Resistance Of ZrO₂/Al₂O₃ Composite Micro-arc Oxidation Ceramic Coating

Aluminum and its alloys have the advantages of good thermal conductivity and high specific strength,and are widely used in the fields of machinery manufacturing,aerospace,automotive parts,construction and bridge construction.In the atmospheric environment,aluminum will form an oxide film on the surface under air oxidation,which is blocked from the surrounding environment.However,the electrode potential of aluminum is relatively negative in the potential sequence.When contacting other metals,aluminum will accelerate its own corrosion as an anode,which is not conducive to the widespread application of aluminum and its alloys.As an advanced surface modification process,micro-arc oxidation is to grow a ceramic film mainly composed of metal oxide on the surface of the metal substrate.The pores of the ceramic film grown in situ are uniform and the structure is dense,which improves the overall performance of the metal.In this paper,through the micro-arc oxidation process,the 2A12aluminum alloy was prepared in the zirconium salt electrolyte to produce ZrO₂/Al₂O₃composite micro-arc oxidation ceramic film.First,the 2A12 aluminum alloy was micro-arc oxidized in different concentrations of zirconium salt electrolyte to prepare ZrO₂/Al₂O₃composite micro-arc oxidation ceramic film;then the samples were corrosion-resistant in 3.5wt.%Na Cl solutions at different PH Sexual testing.The porosity,surface morphology and corrosion resistance of ZrO₂/Al₂O₃ composite micro-arc oxidation ceramic membranes prepared under different zirconium salt concentrations were compared,and the influence mechanism of different zirconium salt concentrations on them was analyzed.The results show that:the surface porosity and micro-pore diameter of the ZrO₂/Al₂O₃ composite micro-arc oxidation ceramic film layer decrease first and then increase with the increase of zirconium salt concentration,and the thickness increases with the increase of zirconium salt concentration;corrosion The current density I_corr increases first and then decreases as the concentration of zirconium salt increases.When the concentration of zirconium salt is 15 g/L,the porosity of the micro-arc oxidation ceramic film reaches a minimum value of 0.856%,the average pore diameter of the ceramic film reaches a minimum value of 0.578μm,and the corrosion current density of the sample I_corr can be reduced by an order of magnitude,electrochemical The impedance modulus|Z|can be increased by 1 order of magnitude.The phase composition of the ceramic membrane layer after micro-arc oxidation treatment is mainly ZrO₂ and Al₂O₃,and changing the concentration of zirconium salt has almost no effect on the phase composition of the ceramic membrane layer.The effect of pH on the corrosion resistance of 2A12 aluminum alloy micro-arc oxidation ceramic coatings was investigated.The results show that:in 3.5 wt.%Na Cl solution,when the pH value is 7,the micro-arc oxidation ceramic coating has good corrosion resistance.When the pH value is 4,it is next,and when the pH value is 10,the corrosion resistance is the worst.Compared with the Al₂O₃ micro-arc oxidation ceramic coating,the ZrO₂/Al₂O₃composite micro-arc oxidation ceramic coating is immersed in 3.5 wt.%Na Cl solution at different pH values for the same time,the corrosion current density I_corr is smaller,the corrosion potential E_corr is larger The resistance R_p is large.This shows that the ZrO₂/Al₂O₃composite micro-arc oxidation ceramic coating has stronger corrosion resistance.