Inhibition of the acid corrosion of iron with haloacetic acids

Abstract

The efficiency of chloro, dichloro, trichloro, bromo, and iodoacetic acids as inhibitors for acid corrosion of iron was studied using polarization technique. A significant retardation of the corrosion rate is observed in the inhibited HNO3 solution. The rate of corrosion depends on the nature of the inhibitor and its concentration and on the temperature of the system. It was found that iodoacetic acid has a significant inhibiting effect on the corrosion of the metal and protection efficiencies approaching 94% were measured. The inhibitor shifts the free corrosion potential in the cathodic direction and polarizes both the cathodic and anodic half reactions. It was found that the compounds under consideration are chemisorbed on the iron surface according to the Frumkin isotherm. The Tafel slope is approximately constant and independent of the concentration of the inhibitor. The thermodynamic parameters of adsorption obtained reveal a strong interaction of these inhibitors on the iron surface.