Corrosion Inhibition of Mild Steel in Acidic Solution by Apricot Gum as a Green Inhibitor

The inhibitive effect of apricot gum AG on mild steel in 0.5 M phosphoric acid solution was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy EIS, linear polarization resistance and electrochemical noise EN techniques. The inhibition efficiency increased with increasing AG concentration up to a certain value and decreased with increasing temperature. Polarization curves indicated that AG acts as a mixed type inhibitor. The EN data were analyzed by statistical and wavelet methods. The results obtained from analysis of EN data was in good agreement with those arising from the polarization and EIS measurements. The adsorption of the inhibitor on the alloy surface in 0.5 M H3PO4 followed the Langmuir isotherm. According to the calculated values of free energy and enthalpy adsorption it was revealed that the adsorption of inhibitor on the steel surface was a combination of physical and chemical adsorption. The morphologies of the uninhibited and inhibited mild steel surfaces in 0.5 M H3PO4 were analyzed by scanning electron microscope SEM. SEM images showed that the alloy surface damage is significantly decreased in presence of the inhibitor.