Adsorption and corrosive inhibitive properties of Vigna unguiculata in alkaline and acidic media

Purpose - To investigate the adsorption behaviour and inhibitive effect of Vigna unguiculata (VU) extract (agricultural waste material) for aluminium corrosion in 0.5 M NaOH and H₂SO₄. Design/methodology/ approach - The inhibitive effect of the plant extract was assessed using weight loss method at 30 and 60^oC. The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition and type of adsorption. Findings - VU extract effectively inhibited aluminium corrosion in both alkaline and acidic media. Inhibition efficiency (I %) of the extract increased with increase in concentration of the extract and temperature. Inhibitor adsorption characteristics were approximated by Freunlich and Temkin adsorption isotherms at all the concentrations and temperatures studied. The phenomenon of chemical adsorption is proposed from the activation parameters obtained. Research limitations/implications - The mechanistic aspect of the corrosion inhibition can be better understood using electrochemical studies such as polarization and AC impedance spectra. Practical implications - The findings may be useful in metal surface anodizing and metal coating. Originality/value - This paper provides new information on the possible application of VU extract as eco-friendly inhibitor. It has not been reported elsewhere.