Protection of Mild Steel in Hydrochloric Acid Through Surface Finishing using HMMT, a Substituted 3-Mercapto-6-Methyl-1,2,4-Triazin(4H)-5-One

The inhibition of mild steel corrosion in 0.5 N HCl by 4-((E)-(4-hydroxybenzilidineamino)-3-mercapto-6-methyl-1,2,4-triazin (4H)-5-one (HMMT), a triazine based Schiff base, at different temperatures have been investigated by weight loss studies, electrochemical screening, surface morphological analysis and basic quantum chemical calculations. Results showed that HMMT is a very good inhibitor for mild steel corrosion in 0.5 N HCl solution. Inhibition efficiency increases with increase in concentration of HMMT and decreases with time and temperature. Polarization studies revealed that HMMT is a mixed type inhibitor with predominant cathodic behavior. Stereomicroscopic and scanning electron microscopic images support the protective action of the inhibitor. Activation parameters suggest the endothermic nature of corrosion process. Quantum chemical calculations were carried out to obtain optimized geometry and vital electronic parameters of the inhibitor molecule.