Effectiveness of 2-mercaptobenzothiazole, 8-hydroxyquinoline and benzotriazole as corrosion inhibitors on AA 2024-T3 assessed by electrochemical methods

Abstract

In this study, the effectiveness of 2-mercaptobenzothiazole (2-MBT), 8-hydroxyquinoline and benzotriazole as corrosion inhibitors for AA 2024-T3 aluminium alloy was evaluated. The corrosion behaviour in the presence of each compound was investigated by image-assisted electrochemical noise analysis, electrochemical impedance spectroscopy, potentiodynamic polarization and the split cell technique. It was found that 2-MBT has superior inhibition properties compared with the other inhibitors. In particular, the specimens immersed in 3.5% NaCl in the presence of 2-MBT displayed high values of noise resistance that were maintained for over 400 h of testing, and high values of low-frequency impedance, measured after immersion for 24 h. The split cell technique and potentiodynamic polarization tests indicated that only 2-MBT decreases significantly both the anodic and the cathodic reaction rates. Scanning electron microscopy observations and energy dispersive X-ray measurements complement the findings from electrochemical measurements indicating that only 2-MBT protects the second phase particles, preventing dealloying, trenching and initiation of corrosion.