Corrosion inhibition of stainless steel 302 by 1-methyl-3-pyridine- 2-Yl–thiourea in acidic media

Abstract

The corrosion inhibition of stainless steel type 302 (302 SS) with different concentrations (0.004-0.007 M) of 1-methyl-3-pyridine-2-Yl–thiourea (MPT) in acid solutions was investigated by potentiostatic polarization measurements. The effect of temperature (283-323±1 K) on corrosion parameters was examined. The open circuit potential values in the presence and absence of MPT noted before and after experiments indicated the formation of passive film on the surface of the samples. It was found that corrosion potential (<i>E</i>_corr) increases with increasing MPT concentrations, while, corrosion current (<i>i</i>_corr) decreases. Inhibition efficiency of MPT is slightly more in 1 M H₂SO₄ than in 1 M HCl. The inhibitor functions through adsorption and follows Temkin isotherm in both the acids. Activation energy (<i>E</i>_a) and Gibbs free energy (<i>∆G</i>_ads) for adsorption of MPT are calculated. The values of <i>∆G</i>_ads decreased (attained more negative values) with increasing temperature.