Dianils as new and effective corrosion inhibitors for mild steel in acidic solutions

The influence of some substituted dianils on corrosion of mild steel in 1N hydrochloric acid and 1N sulphuric acid has been studied using weight loss and electrochemical techniques. Among the five compounds studied, 1,4-dicinnamyledene aminophenylene (DCAP) showed the best performance. All of the compounds showed good inhibition efficiency in both the acids. Inhibition efficiency of these compounds has been found to vary with nature and concentration of these compounds, solution temperature, immersion time and nature of acid solutions. The adsorption of these compounds on the steel surface from both the acids has been found to obey Temkin’s adsorption isotherm. The values of activation energy and free energy of adsorption of all the dianils were calculated to investigate the mechanism of corrosion inhibition. The potentiodynamic polarization studies were carried out at room temperature, according to which all the compounds were found to be mixed type inhibitors and inhibited the corrosion of mild steel by blocking the active sites of the metal.