Evaluating the Performance of Red Onion Skin Extract in 0.2M Hydrochloric Acid as a Green Corrosion Inhibitor for Aluminum

Abstract

The inhibition effect of red onion ethanol extract on the corrosion of aluminium in 0.2M aqueous HCl solution at 303, 313 and 323 K was investigated by weight loss method. The results showed that the inhibition efficiency decreased with temperature rise but increased with the inhibitor concentration from 0.2 to 0.8g/L. The highest inhibition efficiency of weight loss was 80.00% and the lowest was 63.0% as the temperature of the system increased. The activation energy (Ea) for Red onion ethanol extracts values for the blanks in 0.2M HCl were high compared to the values obtained when the extract was introduced into the system at 0.2 to 0.8g/L respectively. Langmuir isotherm provided more accurate description of the adsorption behavior of red onion peel with the R2 values closer to unity. The thermodynamic parameters Kads, ΔHads and ΔSads were determined. The extract of red onion peel increased the life-span of the aluminium hence the half-life of blank was relatively lesser when compared to that immersed in plant extract. Surface characterization methods including FT-IR were used to ascertain whether the plant extract interacted with the aluminium surface, and it was found that the mode of interaction was adsorptive in nature. It could be concluded that the ethanol extract of red onion peel inhibits aluminium in hydrochloric acid solution.