Corrosion Inhibition of Mild Steel in Aqueous Sulfuric Acid Solution Using Heterocyclic Mercapto Compounds – An Experimental and Theoretical Study

The corrosion behavior of iron in 0.1M aqueous sulfuric acid medium has been studied in the presence and absence of: 4-methyl-4H-1,2,4-triazole-3-thiol and 2-mercaptonicotinic acid.Potentiodynamic measurements did not show any shift of corrosion potential toward a more negative potential indicating that these compounds mostly act as mixed inhibitors due to their adsorption on the iron surface.The adsorbed film of these molecules hinders the transport of the metal ions from the metal to the solution and also retards the hydrogen evolution reaction by acting as a physical barrier.The molecules were also studied with the density functional theory (DFT), using the B3LYP functional in order to determine the relationship between the molecular structure and the corrosion inhibition behavior.