Preparation And Corrosion Resistance Of 8-HQ And Silane Modified Micro-Arc Oxide Composite Film Layer On Aluminum Alloy

Aluminum alloy is widely used due to its light weight,high specific strength and easy processing.However,aluminum alloys are prone to corrosion in more corrosive environments such as the ocean.Micro-arc oxidation（MAO）is a common surface treatment technology for aluminum alloys.The MAO film layer obtained has high strength and hardness,and has excellent insulation,wear and corrosion resistance,but its application is limited due to defects such as micro-porosity and micro-cracks on the surface.Based on this point,this work carried out a study on the sealing process of aluminum alloy MAO film layer.The effects of octahydroxyquinoline（8-HQ）conversion treatment,8-HQ conversion combined with silanization two-step treatment and 8-HQ modified silanization one-step treatment on the performance of micro-arc oxidation film layer were investigated,and the optimized sealing process was obtained and the corrosion resistance mechanism was explored.The main results obtained are as follows:（1）The MAO-Al Q₃ film layer was prepared by 8-HQ conversion treatment of the aluminum alloy MAO film layer.Compared with the simple MAO film layer,the composite film layer has significantly enhanced corrosion resistance,and the salt spray resistance time can reach 1200 hours.This is due to the fact that the 8-HQ treatment can form a layer of Al Q₃clusters on the surface of the film,which covers most of the holes on the surface of the film,thus improving the shielding ability of the film against external corrosive media.（2）Two-step treatment of aluminum alloy MAO film layer with 8-HQ conversion treatment and then combined with silanization can further improve the corrosion resistance of the film layer,and the prepared MAO-Al Q₃-KH560composite film layer can have a salt spray resistance test time of 2400 hours.Compared with the simple silane film layer MAO-KH560,the MAO-Al Q₃-KH560 composite film layer is more uniform and flat,the surface pores disappear,the thickness of the film layer increases,and the repair of defects in the film layer is more perfect.This is due to the presence of Al Q₃cluster structure which increases the contact area of MAO film layer with silicon hydroxyl group and increases the surface hydroxyl group content,which makes more silane deposited on the surface of the film layer,greatly improves the physical shielding performance of the film layer.（3）One-step treatment of the aluminum alloy MAO film layer with 8-HQ modified silane hydrolysis solution can also significantly improve the corrosion resistance of the micro-arc oxide film,and the MAO-（Al Q₃+KH560）film layer prepared can withstand salt spray for 1440 hours.However,compared with the MAO-Al Q₃-KH560 composite film layer prepared by step-by-step treatment,there is still a gap,which may be due to the inadequate reaction caused by the simultaneous conduct of both,and the thickness of the prepared silane film is not as good as that of the step-by-step prepared film layer.