Green Corrosion Inhibition of Mild Steel by Xylopia ferruginea in 1 M HCl Solution

The corrosion inhibition potential of alkaloids in Xylopia ferruginea leaves chloroform extract (CE) for mild steel corrosion in 1 M HCl solution was studied using weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation and scanning Electron Microscopy (SEM) techniques. Further fractionation of the CE was carried out in column chromatography, and the subsequent fractions were evaluated as a corrosion inhibitor using EIS and potentiodynamic polarisation studies. The results showed that CE was an excellent corrosion inhibitor up to 94% IE at 500 ppm and the weight loss and electrochemical methods were in good agreement. The Nyquist plots revealed that the charge transfer process mainly controls the corrosion inhibition of mild steel and potentiodynamic polarisation studies showed that the extract behaved as mixed-type inhibitors with predominant anodic effectiveness. Surface morphology studies have shown significant improvements on mild steel surfaces in the presence of the extracts. The adsorption of CE on the surface of mild steel was ideally fitted the Langmuir adsorption isotherm. The Gibbs free energy of adsorption (ΔGads) values range from −29.53 to −26.42 revealed the mechanism of corrosion inhibition is predominantly a spontaneous physisorption reaction. The fractions of the CE leaves showed relatively moderate corrosion inhibition compared to its extract and the %IE of fractions reduced from 80 to 35% and 85 to 59% for potentiodynamic and EIS studies, respectively, after subsequent fractionation processes through column chromatography.