Comparative Analysis of Cystine and Cysteine as Green Corrosion Inhibitors of Aluminium Alloy AA7075-T6

Cystine and cysteine as green corrosion inhibitors of the 7075 aluminium alloy in 0.1 M NaCl solution were analysed and compared. The inhibitive efficiency of the inhibitors was analysed by applying linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) methods. Different concentrations of both inhibitors in NaCl solution were tested under different temperatures and times to determine the corrosion kinetic and thermodynamic parameters. Optical microscopy (OM) and scanning electron microscopy (SEM) were used for analysis of the aluminium alloy surface before and after the electrochemical measurements. The hydrophilicity of the alloy surface with tested inhibitors was compared by applying contact angle measurements. The results showed that cystine and cysteine are effective corrosion inhibitors, with different characteristics and duration of protection on the tested aluminium alloy. Cysteine showed better efficiency for short-term applications while cystine provided more stable protection over a longer period.