Bis-benzothiazoles as efficient corrosion inhibitors for mild steel in aqueous HCl: Molecular structure-reactivity correlation study

Abstract Three different bis-benzothiazole (BBT) derivatives namely 2,6-bis(2-benzothiazolyl)pyridine (BBTP), bis(2-benzothiazolylmethyl)sulphide (BBTMS), and 1,2-bis(benzothiazolyl)ethylene (BBTE) are synthesized and characterized. Corrosion mitigation performance of these bis-benzothiazole derivatives have been inspected for mild steel in aqueous 1 M HCl using electrochemical and gravimetric methods. Corrosion inhibition potentiality of these inhibitors are in the order BBTP > BBTMS > BBTE. This is further substantiated from SEM images. Mixed type corrosion inhibition for all the inhibitors is affirmed from potentiodynamic polarization study. Effect of temperature and exposure time is also evaluated employing gravimetric method. Following Langmuir adsorption isotherm, thermodynamic parameters related to adsorption process are enumerated. Adsorption data together with activation parameters are used to deduce nature of adsorption process of these inhibitors on metal surface. Density functional theory (DFT) and molecular dynamics (MD) simulation are done to explain experimentally obtained result from theoretical view point. Observed corrosion inhibition trend is found to be related to spatial orientation of inhibitor molecules in their most stable energy states in aqueous medium as well as to their intrinsic molecular parameters.