Technical note Influence of molecular structure of substituted benzothiazoles on corrosion inhibition and hydrogen permeation through mild steel in sulphuric acid

Abstract

Aminobenzothiazole and three of its 6-substituted derivatives, namely 2-amino-6-chlorobenzothiazole (ACLBT), 2-amino-6-methoxybenzothiazole, and 2-amino-6-methylbenzothiazole, were synthesised and their inhibition of the corrosion of mild steel in 0·5M H₂S0₄ was investigated by weight loss and some electrochemical techniques. Inhibition efficiencies of various concentrations of these compounds were determined at temperatures in the range 35–60°C. Of the four compounds, ACLBT showed the best performance, giving an inhibition efficiency as high as 97%, even at a very low concentration and at a temperature of 60°C. Potentiodynamic polarisation studies indicated that all four compounds acted predominantly as cathodic inhibitors, with adsorption from H₂S0₄ solutions on mild steel surfaces obeying Temkin's adsorption isotherm. All of the inhibitors were able to reduce hydrogen permeation through the steel surface and performance was enhanced by the addition of iodide ions. Auger electron spectroscopy analysis was also carried out to determine the mechanism of inhibition.