Effects of Thiourea on the Corrosion of Low Carbon Steel in Hydrochloric Acid Solution

The c.orrosion rate of low carbon steel in 4M hydrochloric acid with and w1thout presoence of thiourea has been studied by gravimetric and gasometric methods over the temperature range 303-333 K. The percentage protection of steel increases with the decrease of thiourea concentrations ai various temperature range 303-333 K and approaching highest protect1on (86.82%) at 303K by using I x J0-4 M of thiourea. The high concentration of thiourea (I X l o-3 M). enhances the corrosion rates and act as dcpolariser for the hydrogt:n evolution reaction, with H2S being a product of the chemical depolarisation stage. The H2S is cons.iderecl to be adsorbed in the s-2 H2S- state.: forming activated sites: where anodic dissolution is thereby enhanced. The results wete discussed on basis of adsorption of dissociated thiourea molecules on steel surface. The energies of activation have been cakuJated for the corrosion process of the carbon steel jn acidfrom corrosion rates in the absence and the presence of thiourea.