Electrochemical corrosion performance of friction stir processed cold spray metal matrix composite coatings on AZ31B magnesium alloy under sodium chloride environment

Abstract

Abstract The main objective of this investigation is to study the effect of friction stir processing (FSP) on the surface integrity and corrosion resistance of low-pressure cold sprayed (LPCS) aluminium alloy/aluminium oxide metal matrix composite (Al-Al2O3 MMC) coating deposited on AZ31B magnesium alloy for aerospace and automobile applications. The Al-Al2O3 MMC coating was developed on AZ31B magnesium alloy using a LPCS system. FSP was performed on the MMC coating using a stirring tool made of H13 tool steel. The structural integrity of the coating was analyzed using scanning electron microscopy (SEM). The phase analysis of coating was studied using x-ray diffraction (XRD). The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were performed to study the corrosion resistance of cold sprayed and FSPed samples. Results showed that FSP improved the structural integrity of MMC coating. Both the EIS and potentiodynamic polarisation test results reveal that FSP treated samples provide superior corrosion resistance than cold sprayed samples. This is due to the increase in interfacial bonding between matrix and reinforcement phase. The degree of separation and dispersal of alumina in the Al alloy matrix is increased through the shear force generated by the FSP tool on the coating surface.