Corrosion inhibition of stainless steel type 316L in hydrochloric acid solution using p-aminoazobenzene derivatives

The inhibiting action of some p -aminoazobenzene derivatives towards the corrosion behavior of stainless steel type 316L in 3M HCl has been studied using weight loss, galvanostatic and potentiodynamic anodic polarization techniques. The inhibition efficiency of the investigated compounds was found to increase with increasing the concentration of inhibitor and with decreasing the temperature. The addition of KI to p-aminoazobenzene derivatives increased the inhibition efficiency due to synergistic effect. The presence of iodide ions in the solution stabilized the adsorption of these compounds on the steel surface and, therefore, improved the inhibition efficiency. Inhibition process was explained on the basis of adsorption of these compounds on the metal surface. The degree of surface coverage varied linearly with logarithm of inhibitor concentration fitting Temkin isotherm. Some thermodynamic parameters were calculated and discussed. It was found that, the p -aminoazobenzene derivatives provide a good protection to stainless steel against pitting corrosion.