Enhancing corrosion resistance of Al 5050 alloy based on surface roughness and its fabrication methods; an experimental investigation

The aim of this study is to investigate the effect of roughness fabrication methods on the corrosion resistance of Al-5050 alloy. The surfaces having roughness (0.45–6.2 μm) are generated by polishing, machining, and sandblasting. The surfaces are tested in 3.5wt%NaCl aqua solution with the voltage from −0.2 to 1.0 V with a scan rate of 0.1mv/s. Tafel curves are plotted to determine the corrosion current density (I_corr) and the corrosion potential (E_corr). In addition to this, corrosion behavior is analyzed by the Electrochemical Impedance Spectroscopy (EIS). Before and after corrosion experiments, surface morphology of the samples is analyzed by scanning electron microscope (SEM) equipped with energy dispersive spectroscopy. Also, X-ray Diffraction (XRD) analysis is carried out to investigate the corrosion products present on the surface of the Al-5050 alloy. The results indicate that the corrosion rate is increased with an increase in the surface roughness. The machined max surface shows 21.9% higher corrosion rate compared to the polished surface. Sandblasted surface due to protective layer and homogeneity in surface roughness experiences less corrosion rate than the machined max surface. The larger and deeper grooves in the machined surface lead to severe pitting and higher corrosion. The type of surface roughness plays a significant role in corrosion behavior and cathodic and anodic kinetics.