Synergistic effect of 2-mercaptobenzimidazole and octylphosphonic acid as corrosion inhibitors for copper and aluminium – An electrochemical, XPS, FTIR and DFT study

Abstract Inhibitory action of 2-mercaptobenzimidazole (MBI) and octylphosphonic acid (OPA) and their binary combinations on copper and aluminium in 3 wt.% NaCl was investigated by electrochemical methods, whereas the bonding of inhibitors was scrutinized by XPS and FTIR spectroscopies, wettability measurements, and DFT calculations. MBI is a good inhibitor for Cu but not for Al, whereas OPA behaves complementary. Although OPA is not an inhibitor for Cu, it can synergistically boost corrosion inhibition of copper when added to MBI. Evidence suggests that OPA changes the bonding of MBI by making the copper surface more susceptible to MBI resulting in a thicker and more protective organic film.