Corrosion and Corrosion Inhibition of Mild Steel in H2SO4 Solutions by Zizyphus Spina-Christi as Green Inhibitor

Abstract

The corrosion and corrosion inhibition of mild steel in 1.0 M H2SO4 contg. 10% Et alc.(EtOH) by Zizyphus Spina-Christi (ZSC) exts. (aq. ext. and alc. ext.) has been studied using chem. techniques (hydrogen evolution (HE) and mass loss (ML)) and electrochem. techniques (electrochem. impedance spectroscopy (EIS) and potentiodynamic polarization (PDP)). The effect of acid concn. on the corrosion rate of mild steel increases with acid concn. (0.25-1.5) M showing first order corrosion reaction without changing the reaction mechanism, and the results showed that when the concn. of ZSC exts. (aq. ext. and alc. ext.) increased the rate of steel corrosion is decreased, which indicates that the inhibition of the corrosion process is produced. Electrochem. impedance spectroscopy results showed that the corrosion and corrosion inhibition of steel occurred mainly by charge transfer. The electrochem. results of polarization also showed that the exts. of ZSC plant act as mixed type inhibitors, they retarded both cathodic and anodic reaction. The exptl. results from chem. and electrochem. studies were fit Langmuir isotherm. Values of equil. const. of adsorption Kads and the std. free energy of adsorption ΔGads, for the exts. are calcd. on SciFinder(R)