Solvent Effect and Adsorption Study of Mild Steel Protection from Acid Corrosion Using Eco-friendly Formulations of Annatto Extract

Annatto extract (dye) was investigated as a cheap a nd ecologically friendly alternative corrosion inhibitor. The corrosion process was moni tored with mild steel coupons in 1.0 M hydrochloric acid at temperatures between 30 C to 90 C by weight loss and spectroscopic techniques. The dye effectively inhib ited the corrosion of mild steel in the acid at the studied temperatures. Inhibition effici en y obtained was found to vary with temperature and concentration of the dye. Adsorptio n m dels were used to predict the nature of the dye-steel surface interaction. Thermo dynamic models provided evidence of spontaneous physical and chemical adsorption mec hanism with the evolution of heat. Kinetic studies revealed a deepening effect on the activation potential in the presence of the dye. The effect of solvent and synergistic inte nsifiers on the effectiveness of the dye was also assessed. Heavy metal ion composition in t he formulation was determined and was within the limit of environmental and health sa fety.