Nanosized scale roughness and corrosion protection of mild steel in hydrochloric acid solution and in the presence of Turmeric (Curcuma Longa) Extract as a green corrosion inhibitor: FTIR, polarization, EIS, SEM, EDS, AFM studies, and neural network modeling

AbstractIn this study, the effect of Turmeric (Curcuma Longa) extract (TE), as an environmentally friendly corrosion inhibitor, was investigated in 1 M hydrochloric acid solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Additionally, the proposed inhibitor was characterized by FTIR, and surface morphology of mild steel after and before its exposure to acid solution in the presence and absence of 0.030 g/l TE inhibitor was examined through scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), and atomic force microscopy (AFM) techniques. Effect of TE concentration and temperature was evaluated. Then, thermodynamic parameters have been calculated and adsorption studies have been investigated. A good fit to Freundlich adsorption isotherm was obtained between surface coverage degree and inhibitor concentration. SEM and AFM images and EDS analysis of mild steel specimens in the absence and presence of the TE inhibitor confirmed the protective layer formation on metal surface. Finally, electrostatic interaction between main component of inhibitor and metal surface was investigated. Inhibition efficiency up to 92% has been achieved in 1 M acid solution containing 0.030 g/l inhibitor at 22 °C. Neural network modeling shows low stability of TE by increasing temperature and time.Keywords: corrosiongreen inhibitors, mild steelelectrochemical investigationsscanning electron microscopyatomic force microscopy