Corrosion inhibition of aromatic acids on Al-7075 anode for Al-air batteries with alkaline electrolyte

The severe hydrogen evolution corrosion is the major obstacle for the extensive application of the aluminium-air batteries. In this research, three aromatic acids, i.e. benzoic acid (BEA), iso-phthalic acid (IPA), and trimesic acid (TRA), are performed as corrosion inhibitors for Al-7075 alloy in 2 M KOH water-ethanol (volume ratio 8:2) solution. The results reveal that all of the three aromatic acids are excellent inhibitors for Al-7075 alloy in alkaline medium with the following inhibition efficiency order: BEA > IPA > TRA, and the peak value of inhibition efficiency is 43.7% when 5 mM BEA is added. The addition of aromatic acids significantly improves the discharge characteristics of the Al-air battery, which increases the capacity density (1357.47 mA cm⁻²) and anode utilization (45.6%) remarkably. The results of Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) demonstrate that the protective film, which is composed of Al salts of organic acid (RCOO-Al), is adsorbed on the Al-7075 alloy surface through chemical bonds between Al substrate and the O atoms on C[dbnd]O groups, which enhances the corrosion and electrochemical characteristics of the Al-7075 anode for Al-air battery with alkaline electrolyte.