Effects of anodization and micro-arc oxidation coatings on corrosion resistance and mechanical properties of 5A06 aluminum alloy
[Introduction]The effects of different oxidation coatings on the corrosion resistance and mechanical properties of 5A06 aluminum alloy need to be studied.[Method]The corrosion behaviors of anodized and micro-arc oxidized 5A06 aluminum alloy in seawater and the variation of their mechanical properties after corrosion were examined by steady-state immersion corrosion test and stress corrosion test.[Result]The pitting corrosion was predominant for 5A06 aluminum alloy and its oxidation coatings in seawater.Both micro-arc oxidation coating and anodization coating exhibited good corrosion resistance.The results of potentiodynamic curve measurement and electrochemical impedance spectroscopy showed that the corrosion potentials of bare,anodized,and micro-arc oxidized 5A06 aluminum alloy specimens were shifted significantly toward the negative direction after 30 days of immersion in seawater,their corrosion current density and passivation current density were increased,and their charge transfer resistance was decreased,indicating a decline in corrosion resistance.The micro-arc oxidation coating exhibited the lowest corrosion current density and passivation current density,and the highest charge transfer resistance among all the specimens,indicating that the corrosion resistance of micro-arc oxidation coating is superior to that of bare aluminum alloy and its anodization coating.Stress-strain test results and fracture micromorphology observation showed that the reduction of elongation after fracture and section shrinkage after stress corrosion test were 13.79%and 6.72%,respectively,for the micro-arc oxidation specimen,both of which were smaller than that of the anodization specimen,indicating that the micro-arc oxidation coating had better plasticity and toughness.[Conclusion]Under the coupled effects of stress and seawater corrosion,the corrosion resistance and mechanical properties of 5A06 aluminum alloy exhibit a certain degree of degradation.Both micro-arc oxidation and anodization coatings can improve the corrosion resistance of 5A06 aluminum alloy,in which the micro-arc oxidation coating demonstrates superior corrosion resistance and mechanical properties.
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