Long term durability studies on the corrosion inhibition effect of 2-mercaptobenzimidazole (C₃H₄N₂S) on AA6022: Mechanism of film formation and influence of IMPs

Abstract

This study explores stability and variations of a mercaptobenzimidozole-inhibitor-based film upon the surface of Al alloy AA6022 and its contribution to the long-term corrosion inhibition in 0.1 M NaCl. Results provide a deeper insight and understanding of the mechanisms of combined inhibitor film formation and oxide layer growth, up to 240 h exposure, and the effect that the intermetallic particles have on the resultant film stability within these regions. Electrochemical impendence spectroscopy (EIS), potentiodynamic polarization (PDS) and X-ray photoelectron spectroscopy (XPS) studies reveal the formation of a porous, defective oxide layer on the alloy surface under uninhibited conditions. The addition of inhibitors results in the creation of a cathodically controlled system and the formation of a thin inhibitor-oxide mixed film, through the chemical absorption of inhibitor molecules to the substrate via S atom in association with O, thus reducing the corrosion rates. Focus ion beam scanning electron microscopy further confirms the presence of a combined oxide layer and inhibitor film, which covered both the alloy matrix and intermetallic regions. In addition, activity reduction of the Fe rich IMPs is thought to have occurred. Show more