Adsorption Action of Phosphine Inhibitors on the Corrosion of Steel

摘要

Phosphine compounds were investigated for their possible use as acid corrosion inhibitors. Electrochemical, weight loss and gasometry methods were employed to study the protective effect of triphenyl phosphine (TPP) and carboethoxy methylene triphenyl phosphorane (CMTPP). The inhibiting effect of TPP is estimated as 100% for an inhibitor concentration of 0.0005 M. Potentiodynamic polarization data indicate that both compounds act predominantly as cathodic inhibitors. The maximum inhibition efficiency was afforded by CMTPP at low concentrations, whereas at higher concentrations the protection efficiency of TPP increases. This was discussed on the basis of steric hindrance. The mode of adsorption of the inhibitors on the steel surface is proposed, as well as empirical kinetic equations based on the cathodic reaction. These were supported by fitting the experimental data to the Temkin adsorption isotherm and to the thermodynamic/kinetic model of adsorption. The free energy of adsorption, the binding constant, the lateral interaction and the number of active sites are reported and discussed.