Experimental investigation of the effect of micro-arc oxidation coating on Al-5456 alloy

The paper presents the parametric impacts of micro-arc oxidation (MAO) process on coating growth, thickness, surface roughness, microhardness, thermal shocks and corrosion resistance of MAO coated Al-5456 alloy in KOH+Na2SiO3 electrolytic solution.The characterisation of coating surfaces was analysed through FESEM, EDS mapping and XRD images.The MAO coating is mainly composed of SiO2 and Al2O3 in -Al2O3 and -Al2O3 phases.Applied voltage, oxidation time and inter-electrode gap were found out to be significant parameters as far as coating growth; thickness, microhardness and surface roughness are concerned.The MAO coating synthesised at 290 V did not loss the adhesion strength even with increase in number of thermal shocks at 823 K. Corrosion resistance of MAO coated surface was found 8.34 times greater than that of uncoated surface.Optimal parametric setting could be secured for MAO coating of Al-5456 alloy for the application in areas such as marine, automobile and space industries.