Use of Compounds Containing Heteroatoms as Electrochemical Corrosion Inhibitors for Copper in Hydrochloric Acid

The corrosion inhibition characteristics of N-[(Z)-1-phenylemethyleidene]-N-{2-[(2-{[(Z)-1phenylmethylidene]amino}phenyl)disulfanyl]phenyl} amine and N-[(Z)-1-(4-methylphenyl) methylidene]-N-{2-[(2-{[(Z)-1-(4methylphenyl) methylidene] amino}phenyl) disulfanyl] phenyl}amine on copper in HCl 15% solution was investigated using polarization and impedance methods. Electrochemical measurements indicate that Schiff bases have good inhibiting properties with mean efficiency of 98% at 0.5mM concentration of inhibitors on copper corrosion in acid media. Tafel curves show that Schiff bases shifted the corrosion potential towards more positive values. Therefore, these compounds mainly affect the anodic process and decrease the corrosion rate. Impedance measurements for two Schiff bases show an increase of charge transfer resistance with increase of inhibitor concentration. The adsorption of Schiff bases on copper obeys the Langmuir adsorption isotherm. The negative values of Delta G(ads) indicate that the inhibitors are strongly adsorbed on the copper surface. Other thermodynamic parameters (Delta H-ads, Delta S-ads) of the Schiff bases have been calculated.