Corrosion protection of zinc alloy ZA12 using anodizing process in acidic media

Abstract

Zinc alloys are used in very wide industrial applications due to their excellent physical and mechanical properties. To improve the corrosion resistance, anodizing process is used. Anodizing of Zinc Alloy ZA12 is investigated in 1 M H2SO4 solution for 10, 20 30,40 and 50 mins at a constant voltage of 5V. Atomic force microscope (AFM) used to study the surface roughness of the anodic film. The results show that the surface roughness of anodic film is primarily depending on the anodizing time and coating average thickness. Furthermore, the microhardness also increases with the anodizing time. The corrosion performances in sea water of both anodized and non-anodized zinc specimens are acquired by potentiostatic polarization. Corrosion current density (iCorr) and corrosion potential (ECorr) are obtained from potentiostatic polarization studies. The studies show that the corrosion current density and corrosion rate were reduced with increasing the anodizing time which enlarges anodic film average thickness. The results of corrosion rates indicate an enhancement in corrosion resistance of anodized Zinc Alloy ZA12 in the sea water. Contact angle test measurements for ZnO layer formation on zinc alloy AZ12 were detected which indicate that the contact angle of un-anodized film seems to be elevated than that of anodized film after sealing the anodic film.