The protection mechanism offered by Heterophragma adenophyllum extract against Fe-C steel dissolution at low pH: Computational, statistical and electrochemical investigations

Abstract An ethanolic extract of Heterophragma adenophyllum (HA) was investigated as corrosion inhibitor for Fe-C steel in hydrochloric acid. The inhibition effect of HA extract was examined using the weight deterioration, electrochemical impedance spectroscopy (EIS) and polarization techniques. EIS showed enhanced charge transfer resistance with maximum protection value of ∼96% at 600 ppm concentration. Tafel extrapolation results revealed that corrosion was restricted by mixed inhibition. The icorr values reduced considerably from 53.63 μA cm-2 at 100 ppm to 20.11 μA cm-2 at 600 ppm of HA extract. Interaction intensity was further examined through Langmuir, Freundlich, D-R, Frumkin, and Flory-Huggins adsorption isotherms. The computational study, statistical modelling and surface morphology by XPS, AFM, and SEM-EDX, indicated an excellent adsorption capability of HA on Fe-C steel.