A study on inhibition efficiency of (-)-corey lactone diol as corrosion inhibitor for low carbon steel, in hydrochloric acid: Surface characterisation and quantum studies

Corrosion inhibition efficiency of expired (-)-Corey Lactone Diol (CLD), a pharmaceutical agent used for the treatment of hypertension, was checked towards the corrosion of mild steel in hydrochloric acid media. Corrosion study was conducted at different inhibitor concentration and also at different temperature. The inhibition performance of CLD was measured by chemical and electrochemical methods such as tafel extrapolation and electrochemical impedance spectroscopy. From the study, it has been found that the CLD is an efficient corrosion inhibitor for mild steel in hydrochloric acid media with an inhibition efficiency of 90% at 600 ppm. Influence of temperature on corrosion inhibition performance of the indicator was measured and the data indicates the inhibition happen by means of adsorption and it follows temkin adsorption model. Tafel polarisation study suggests the mixed type of inhibition nature for CLD. Increase in Resistance polarisation (Rp) and decrease in Cdl value from the EIS study further confirms the protective nature of the inhibitor. Tabulated thermodynamic parameters for corrosion process indicate the spontaneity of adsorption. Surface morphological study was done by SEM and EDX which showed the protective layer formation on the metal surface.