Moringa oleifera as an eco-friendly corrosion inhibitor for carbon steel in hydrochloric acid solution

The impact of aqueous extract of Moringa oleifera on the carbon steel dissolution in hydrochloric acid was investigated by chemical (mass loss) and electrochemical [potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM)] techniques. Atomic force microscope (AFM) and Fourier Transforms Infrared Spectra (FTIR) surface analysis techniques were used to illustrate the importance of this green Moringa oleifera extract in the corrosion inhibition process for carbon steel. The results demonstrated that the Moringa oleifera extract mitigates the corrosion of carbon steel in 1 M HCl. From the mass loss test, it was found that with an increase in the concentration of Moringa oleifera extract up to 600 ppm, the inhibition efficacy increased to 91.7% at 25 degrees C, indicating that this extract is an excellent inhibitor for carbon steel in HCl medium. It was found that the inhibition efficacy decreased with raising temperature, indicating that the extract was adsorbed physically on carbon steel surface according to the Langmuir adsorption isotherm. The parameters of activation and adsorption processes are computed and discussed. Polarization data revealed that this extract behaved as a mixed kind inhibitor. Charge transfer resistance (R-ct) increased, while double layer capacitance (C-dl) decreased upon addition of the extract. A mechanism of the corrosion inhibition of carbon steel by Moringa oleifera extract was proposed and discussed.