Insights into the effectiveness of natural Mentha oil in mitigating the corrosion of carbon steel in sulfuric acid

The efficacy of Mentha oil as a safe and environmentally acceptable anticorrosion agent for X65 carbon steel (X65 CSt) in 1.0 M H2SO4 solutions was confirmed using chemical, electrochemical, and computational techniques. The anticorrosion efficacy rises with increasing Mentha oil dosages and reaches 98.26% at 500 mgl–1 using potentiodyanmic polarization (PDP). Mentha oil operates as a mixed inhibitor by retarding the anodic dissolution of steel and the cathodic hydrogen evolution. Electrochemical impedance data confirmed that X65 CSt corrosion is under charge transfer control and the adsorption of Mentha oil on the steel surface led to the formation of protective film. The inhibitory mechanism has been established by the spontaneous adsorption of the significant oil components onto the X65 CSt surface owing to the negative values of free energy of adsorption. The adsorption process is controlled by the Langmuir isotherm. Mentha oil inhibits X65 CSt from pitting in solutions involving chlorides by moving the pitting potential to the positive directions. Furthermore, Monte Carlo and DFT calculations were executed to study the reactivity of Mentha oil molecules and their tendency to adsorb on Fe(110) surface.