Characterization and corrosion behavior of anodized Aluminum alloys for military industries applications in artificial seawater

The corrosion behavior of the hard anodizing coating layer, formed on Aluminum alloys in sulphuric acid electrolyte containing sodium lignin sulphonate, was investigated by using salt spray procedure and Potentiodynamic polarization technique, in 3.5% sodium chloride solution. The anodic process was performed on different groups of Aluminum alloys as Al2014, Al6061 and Al7075, which are used in military industries. The results showed that the corrosion resistance and the anodized coating layer are influenced by the type of the alloy and the anodizing conditions such as current density, acid concentration and time of duration. Moreover, changes in film thickness, anodic coating weight and hardness of Aluminum alloys have been studied and the obtained results were compared and analyzed. Adsorption of sodium lignin sulphonate on oxide surface has been confirmed by Fourier transform infrared spectroscopy (FTIR). The phenolic and carboxylic groups in lignin inhibitor are responsible for forming a complex on the metal oxide surface, that improves the corrosion resistance.