Investigation the Effect of Voltage on the Microstructure and Corrosion Behavior of 5083 Aluminum Alloy Anodizing Coating

For decades, aluminum alloys have been known as one the most vital materials utilized in diverse fields of industry. In spite of significance, Al alloys can be easily exposed to corrosion. In this study, it has been tried to investigate anodic oxide coating made by hard anodizing of 5083 aluminum alloy in sulfuric acid at the temperature of 0 ºC and different voltages (20, 27 and 35 V). Subsequently, all samples were characterized using X- Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Field Emission Scanning Electron Microscope (FESEM). Low angle XRD results showed that the amorphous alumina coatings were formed in the surface of the samples. SEM images showed that the coatings are porous which is directly related and affected by anodizing voltage. FESEM images of fracture surfaces were indicant of formation and growth of oxide nano-cells in the cross section of the coatings. In order to investigate the properties of the coatings, micro-hardness, roughness and thickness measurement was carried out. Results showed that micro-hardness, roughness and thickness of the coatings increase by increasing the anodizing voltage. Furthermore, potentio dynamic polarization and electrochemical impedance spectroscopy (EIS) tests were performed. Electrochemical analysis proved that by increasing the anodizing voltage, corrosion resistance of the samples declined due to increasing the porosities on the surface of the coatings.