Electrochemical Corrosion Performance of Twin Wire Arc Sprayed Aluminium Coatings on AZ31B Magnesium Alloy under Sodium Chloride Environment
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Abstract
Magnesium alloys are used for various industrial applications because of their exceptional properties like low weight-to-strength ratio, stiffness and density. The twin wire arc spray (TWAS) technology is extensively implemented in coating technology for preventing structures and parts from corrosion because of its viability. The research work focuses on studying the impact of the microstructure and corrosion behaviors of twin-wire arc-sprayed (LPCS) aluminium (AA2024) coating on the AZ31B magnesium alloy. A high-hardness, low-porosity coating was successfully prepared at optimum conditions of 5 kW power, 3.5 bar air pressure and 200mm standoff distance and the corrosion properties of the coating were investigated. The morphology and microstructure studies were carried out by SEM and XRD, where a compact with a low porosity coating has been achieved. Also, the corrosion behaviour of the deposition was studied through open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) analysis, where a simulation of an industrial environment that contained sodium chloride ions to induce corrosion was utilised. The corrosion rate observed was 1.15 mm/year. Both the EIS and potentio-dynamic polarisation experiments indicate that the Mg alloy with aluminium coatings enhanced the coating corrosion resistance after exposure. Morphological analysis showcases a layer of passive film on the surface of the coating, which is believed to act as a protective layer against corrosion.
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