Insight into the corrosion resistance of mild steel in an acidic environment in the presence of an organic extract: Experimental and computational approach

Abstract

Green corrosion inhibitors are crucial in lowering the rate at which metals corrode as well as the negative environmental effects of hazardous substances. Considering this, Curcuma longa (CL) root extract was used as an effective and safe corrosion inhibitor in this study. The inhibitory efficacy was thoroughly investigated using the weight loss (WL), open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) techniques, respectively. The inhibitor was found to be effective at impeding the rate of deterioration of mild steel in 1 M HCl and 0.5 M H 2 SO 4 environments. In a mixed-type mode, the CL reduced the anodic and cathodic reactions. However, in a 0.5 M H 2 SO 4 environment, CL proved to be slightly more effective compared to a 1 M HCl environment. Inhibition efficiency values of 91.8 % (0.5 M H 2 SO 4 ) and 89.6 % (1 M HCl) were obtained. The Langmuir adsorption isotherm (LAI) was used to validate the results. Some surface probe analysis such as scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FR-IR), and X-ray photoelectron spectroscopy (XPS), were used to complement the electrochemical results. Quantum chemical computations confirmed some active sites on the molecular structures of a few selected active constituents of the CL extract. • The inhibitory mechanism was influenced by the nature of acid anions. • CL extract displayed significant inhibition effect especially in 0.5 M H 2 SO 4 environment. • Polarization studies reveal that CL functioned as a mixed type inhibitor. • Improved surface morphology was confirmed by SEM, XPS and AFM studies. • DFT calculation reveal the adsorption sites on the selected constituents.