Evaluation of Millet Extract as Green Inhibitor for AA6063 Corrosion in 1 M KCl: From Electrochemical Studies to Optimisation

This study presents a comprehensive evaluation of millet extract as a green corrosion inhibitor for the protection of AA6063 in a 1 M KCl solution medium. The research integrates multiple electrochemical techniques, including open circuit potential (OCP) measurements and linear sweep voltammetry (LSV), alongside detailed adsorption studies. These are further complemented by the application of response surface methodology (RSM) to enhance and optimize the inhibitor’s performance. A central composite design (CCD) was strategically employed to systematically vary key experimental parameters, specifically, the concentration of millet extract and the operating solution temperature. The electrochemical investigations provided deeper insights into the underlying inhibition mechanism, while the RSM framework enabled the identification of optimal operating conditions for corrosion control. The resulting second-order polynomial model was rigorously validated through analysis of variance (ANOVA), which confirmed the statistical significance and strong influence of both concentration and temperature on the corrosion rate. The optimal conditions were determined at a concentration of 0.284 g and a temperature of 33.56 ºC, resulting in a low corrosion rate of 0.332 mm yr–1. This study concludes that millet extract is an effective and environmentally friendly corrosion inhibitor, offering a viable, sustainable alternative to conventional chemical inhibitors in corrosion prevention strategies.