Corrosion inhibition of L-tryptophan on Al-5052 anode for Al-air battery with alkaline electrolyte

In the present work, the inhibition effect of L-tryptophan for Al-air battery in 4 M NaOH solution was evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and the hydrogen evolution experiments. The outcomes suggest that L-tryptophan behaves as an efficient corrosion inhibitor for Al-5052 and the anode utilization rate is as high as 90.76% at 0.09 M inhibitor concentration. PDP studies reveal that the presence of L-tryptophan affects the Tafel reactions and shifts the corrosion potential significantly. L-tryptophan behaves predominantly as a cathode-type inhibitor. Moreover, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), contact angle, and atomic force microscopy (AFM) techniques were used to investigate the adsorption of L-tryptophan on Al-5052 substrate. According to anode weight loss, the mass capacity and energy densities rose in the presence of L-tryptophan from 990.1 mAh g⁻¹, 1317.2 Wh kg⁻¹ to 2702.7 mAh g⁻¹ and 4094.6 Wh kg⁻¹, respectively.