Study the Stability of A 356 Al Alloy/ZrO2 Composites Fabricated by Vortex and Squeeze Casting in Acid Rain

Abstract

Electrochemical behavior of A 356 Al alloy and its composites reinforced by zirconia and prepared by vortex and squeeze casting was studied in acid rain using open circuit potential, poteniodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. The open circuit potential for the A 356 alloy and its vortex cast composites increases in noble direction very slowly with time till reaches a steady state value indicating growth of the pre-immersion passive oxide film on the tested materials in the acid rain to a certain thickness which increases with increasing of the zirconia content of the composites. Also, the open circuit potential values for the squeeze cast composites are higher than that for vortex composite. This means that the surface of squeeze composite allows for formation passive film with large thickness than that formed on vortex one. The results of polarization and EIS indicated that the corrosion resistance of the vortex composites increases with the increase in the vol. % of ZrO2 up to 20 % then decreases again. Also, the corrosion resistance of the squeeze composites increases as the squeeze pressure increases. Additional, the micrographs of scanning electron microscopy (SEM) well-showed that the surface of squeeze composite is covered by a passive film and less exposure to corrosion in comparing with the surface of vortex composite. Energy dispersive spectroscopy (EDS) found out the presence of a protective passive aluminium oxide on the two types of the test composites in acid rain.