Corrosion Inhibitory Effects of Some Substituted Thiourea on Mild Steel in Acid Media

Mass loss and thermometric methods have been used to study the inhibition of mild steel corrosion in HCl and H 2SO 4 solution by the pyridyl substituted thiourea compound 1-(2,6-diazene)–3–benzyl thiourea (ST 1), 1–(3’-pyridyl) – 3 – benzyl thiourea (ST 2), 1 – (3’- pyridyl) – 1 –phenyl thiourea (ST 3), 1–(2’- pyridyl)–3–phenyl thiourea (ST 4). Values of inhibition efficiency obtained from the two methods are in good agreement with each other and are dependent upon the concentration of inhibitor and acid. The difference in the inhibition behaviour of the compounds have been explained in terms of the solubility of the substituted thiourea compounds and strength of the inhibitor-metal bond. Inhibition efficiency of all inhibitors increas with increasing concentration of inhibitor. Inhibition efficiency is more in case of H 2SO 4 rather than in HCl. Inhibition efficiency was found maximum upto 99.26% for mild steel in H 2SO 4 solution. Inhibition efficiencies of synthesised substituted thiourea have been found much more than their parent thiourea.