Inhibitive effect of L-OH on the corrosion of austenitic chromium-nickel steel in H2SO4 solution

The corrosion behavior of the austenitic chromium-nickel steel in different concentrations (0.001, 0.002, 0.005, and 0.01M) of dimethyl 2-(2-hydroxy phenyl amino)-3-(triphenyl phosphoranilidin) butane dioate (L-OH) in 0.5M H2SO4 was investigated by potentiostatic polarization measurements. The effect of concentration and temperature on inhibition properties was determined. It was found that the presence of L-OH reduces markedly the corrosion rate of steel in the acid solution. The inhibition efficiency increases as the L-OH concentration is increased. Maximum inhibition efficiency (95%) was obtained for alloy in acid solution containing 0.01M of L-OH. Thermodynamic parameters for adsorption of L-OH are calculated. It was found that the inhibitor is adsorbed on the steel surface and the experimental results are in agreement with Timken's isotherm. Negative values of the free energy of adsorption were obtained indicating the spontaneity of adsorption process. Scanning electron microscopy was done from the surface of exposed sample indicating uniform film on the surface of the alloy.