INHIBITION OF THE CORROSION OF IRON BY OXYGEN AND NITROGEN-CONTAINING COMPOUNDS

Corrosion inhibition by quinine, ephedrine, brucine, cinchonine, codeine, and harmaline with respect to the dissolution of iron in 2 M sulphuric acid was measured using electrochemical methods. Polarization curves indicated that these compounds act as mixed-type inhibitors, i.e. both the cathodic and anodic curves are affected. The observed effect follows the Temkin adsorption isotherm. The effect of the different structural features of these compounds on their inhibition efficiency has been studied. Results indicate that the rate of corrosion of iron increases with increasing temperature over the range 30-50 degrees C both in the absence and in the presence of inhibitors. Some thermodynamic functions were also computed and are discussed.