CORROSION INHIBITORS FROM PLANT EXTRACT AND TEREPHTHAL AMIDE DERIVED FROM WASTE PET BOTTLES FOR MILD STEEL IN ACIDIC MEDIUM

ABSTRACT Powdered Cassia Siamea leaves were investigated as a possible corrosion inhibitor for mild steel in 2 M HCl. Terephthal amide obtained from depolymerizing waste PET (Polyethylene terephthalate) bottles through aminolysis using mono ethanol amine (MEA), served as an additive to improve the efficiency of the powdered leaves. The plant inhibitor was prepared by dissolving 1.5 g of the powdered leaves in 300 ml of 2 M HCl and boiled for 3 hours. Corrosion rates of the steel samples were determined using both electrochemical analysis and weight loss measurements. The powdered leaves and terephthal amide were characterized using Fourier Transform Infrared Spectroscopy (FTIR). Phytochemical screening was conducted on the powdered leaves to verify the presence of heterocyclic compounds such as tannins and flavonoids since they are known to have inhibitive properties. Results obtained from electrochemical readings show a reduction in corrosion rate (CR) with increasing plant inhibitor volume concentrations. The CRs decreased even further with the addition of the terephthal amide thereby increasing the inhibitor efficiency (IE %) of the plant inhibitor. It was observed from the polarization curves that the cathodic reactions were inhibited more as compared to the anodic reactions and therefore the inhibitor can be classified as a cathodic inhibitor. The CRs obtained from weight loss measurements also show a reduction in rates with increasing concentration, corresponding to the electrochemical readings. Less weight was also lost with increasing inhibitor concentration. The phytochemical screening confirmed the presence of tannins, saponins and flavonoids in the powdered leaves. The FTIR also confirmed the presence of heterocyclic compounds and amides in the powdered leaves and terephthal amide respectively.