Extended protection of mild steel in molar HCl using the Garcinia Indica fruit rind extract (GIW) and iodide ions; electrochemical, thermodynamic and kinetic studies

The extended protection of mild steel in hydrochloric acid (HCl) media at four different temperatures using the synergistic interaction of a nontoxic, green corrosion inhibitor Garcinia Indica fruit rind (GIW) and potassium iodide (KI) is discussed in this paper. The investigations are mainly carried out using weight loss and electrochemical studies. The corrosion inhibition property of the aqueous extract is due to the presence cyanidin anthocyanins such as cyanidin 3-glucoside and cyanidin sambubioside and o-hydroxy citric acid. By the addition of 200 ​ppm of KI to 4% GIW extract, the efficiency increased from 89% to 90% at 303K but the increase is appreciable at 333K from 74% to 81%. The results explain the charge transfer controlled reactions of corrosion inhibition and proves the mixed type characteristic of GIW/KI pair. The adsorption process is found to be mainly the physisorption of GIW/KI pair. Monte-Carlo simulations of the constituent molecules reveal an increase in binding energy when GIW adsorbed along with KI. [Display omitted] •GIW/KI pair acts as synergistic pair improving the protection capacity of MS.•The temperature and inhibition capacity are inversely related.•The EIS studies support the charge transfer controlled inhibition of GIW/KI pair.•The Monte Carlo simulations show the pattern of adsorption.•The best-fit isotherm is the Langmuir model.