Corrosion Inhibition of Cocamidopropyl Betaine on Aluminum 1050 Anode for Aluminum Air Battery with KOH Electrolyte

This work addresses the issue of anode corrosion in an aluminum-air battery operating with aqueous alkaline electrolytes. To avoid this problem, an additive known to be an amphoteric surfactant was used. To this end, the surfactant cocamidopropyl betaine (CAPB) was examined as a corrosion inhibitor for the anode of the aluminum-air battery in a 1 M KOH solution. This investigation includes various techniques such as gravimetric measurements, potentiodynamic polarization, electrochemical impedance, surface analysis, and theoretical calculations. The gravimetric tests have shown that the corrosion rate (CR) of aluminum significantly decreases with the addition of CAPB molecules. Polarization curve analysis shows that CAPB acts as a cathodic inhibitor, and EIS data indicate a notable increase in polarization resistance with higher inhibitor concentration. Electrochemical results indicate that the CAPB additive provides substantial anticorrosion protection. At its optimal concentration, CAPB achieves an inhibition efficiency of 84.73%, and even at elevated temperatures (55 degrees C), the efficiency remains around 70%. CAPB adsorption follows the Langmuir isotherm, combining both physisorption and chemisorption, with a primary emphasis on physical adsorption. To assess the inhibitory effect of the CAPB additive, the surface features and depth profiles are analysed. The formation of a surfactant-based layer is confirmed through FTIR-ATR. Based on the review of the various experimental and theoretical results, a mechanism of inhibition of the surfactant CAPB is proposed.