Effect of P-Phenylediamine on the Corrosion of Austenitic Stainless Steel Type 304 in Hydrochloric Acid

The effect of P-Phenylediamine on the corrosion behaviour of 304 stainless steel in 3M Hydrochloric acid solution contaminated with 3.5 % sodium chloride was investigated using weight loss and potentiostatic polarization techniques. Corrosion parameters such as anodic and cathodic Tafel slope constants, corrosion potential, corrosion current, corrosion current densities, surface coverage and inhibition efficiency were calculated. The polarization measurements indicated that the inhibitors are of mixed type and inhibit corrosion by adsorption on the surface of steel due to the presence of more than one active centre in the inhibitor molecule. The inhibition effect ranged from 38.1 % to 81.9% maximum at a concentration of between 0.125 % to 1 % before dropping sharply to between 9 % and 4% at 1.25 % to 1.5 % concentration. The adsorption obeyed Langmuir adsorption isotherm up to 1% inhibitor concentration