Electrochemical performance of aluminium alloy in strong alkaline media by urea and thiourea as inhibitor for aluminium-air batteries

Abstract

The corrosion behaviour of aluminium alloy anode was investigated with urea and thiourea in 5 M KOH solution. Measurements were performed under various conditions using chemical (hydrogen gas evolution test) and electrochemical techniques containing Tafel polarization, electrochemical impedance spectroscopy (EIS) and galvanostatic discharge. Also Fourier transform infrared spectroscopy (FT-IR) and atomic force microscopy (AFM) techniques were used to study of corrosion inhibition mechanism and aluminium anode surface morphology. The consequences established that urea and thiourea as additives prevent the corrosion of anode in alkaline electrolyte due to adsorption of their molecules on the aluminium alloy surface. The corrosion inhibition efficiency of aluminium alloy in 5 M KOH in the presence of 25 mM urea and thiourea was investigated by gas hydrogen evolution method, Tafel polarization and EIS techniques. By data analysis of the above three methods, the corrosion inhibition efficiencies for the aluminium alloy were obtained 51.5, 56.3 and 57.1% for urea and 57.0, 60.8 and 62.9% for thiourea, respectively. Also the anodic utilization of the aluminium alloy anode in electrolyte with urea (85.4%) and thiourea (86.1%) is higher than of aluminium alloy in blank solution (83.5%). It is clear from the results aluminium alloy anode has a good discharge plateau at low potential. Therefore, aluminium alloy presented a good discharge performance in 5 M KOH solution in the presence of additives. The results obtained by Tafel polarization, electrochemical impedance spectroscopy and hydrogen gas evolution test techniques were in acceptable agreement with each other and shows this alloy can used in aluminium-air battery.