APPLICATION OF THE KINETIC-THERMODYNAMIC MODEL FOR INHIBITION OF ACIDCORROSION OF STEEL BY INHIBITORS CONTAINING SULFUR AND NITROGEN

Corrosion inhibition characteristics of four selected S-alkylisothioro nium halides on steel in sulfuric acid (H2SO4) media were investigated at 30 degrees C, 40 degrees C, 50 degrees C, and 60 degrees C. The nu mber of active sites on the metal occupied by a molecule of the inhibi tor (1/y) and the binding constants (K) of the inhibitor to the active sites were calculated at the different temperatures. Activation free energies, enthalpies, and entropies for the inhibition processes were determined from rate-constant data measured at 30 degrees C, 40 degree s C, 50 degrees C, and 60 degrees C at two fixed inhibitor concentrati ons. Data were compared and fitted to a published kinetic-thermodynami c model. Results were compared with fits obtained from application of Langmuir, Frumkin, and Flory-Huggins isotherms. Results also were corr elated to the chemical structure of the inhibitors, the length of the alkyl chain of the cation, and the type of the anion.