Corrosion inhibition of mild steel in acidic solution by apricot gum as a green inhibitor

Abstract

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 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 achieved by 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 both free energy and enthalpy of 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 which were analyzed by scanning electron microscope (SEM) showed that the alloy surface damage is significantly decreased due to the presence of inhibitor. © Institute for Color Science and Technology.