Effect of Heat Treatment and Inhibitor on Corrosion Behavior of AISI 4140 Steel

Heat treatment effect on corrosion behavior of AISI 4140 steel and thiourea inhibition action on corrosion of AISI 4140 steel in as bought as well as heat-treated conditions such as annealing, normalizing, hardening and tempering in 1N HCl solution at room temperature was investigated using potentiostatic polarization technique. Results shows that heat treatment has negligible effect on the corrosion behavoiur of steel in comparison with the as bought specimen. Different concentrations of thiourea are used in 1N HCl solution. Inhibition efficiency of thiourea is concentration dependent. Inhibition efficiency increases with a increase in concentration up to a critical concentration. Thermodynamic studies have confirmed that adsorption of inhibitor adopted Temkins ' adsorption isotherm and physisorption process controls the inhibition.