Electrochemical Studies of 3,3'-Dimethylbiphenyl-4,4'-diamin C14H16N2 ( O.Tolidine) On Carbon Steel Corrosion in Hydrochloric Acid Medium

Abstract

The corrosion behavior of C38 steel in Hcl solution with different concentration of 3,3'-Dimethylbiphenyl-4,4'-diamin (O.Tolidine)(OT) ,was investigated by weight loss and electrochemical measurements. The effect of temperature on the corrosion behavior with the addition of (OT) was studied in the temperature range 298–328 K. Results obtained reveal that (OT) performs excellently as good corrosion inhibitor for C38 steel in 1.0 M Hcl. Potentiodynamic polarization studies have shown that (OT) behaves as mixed-type inhibitors. The inhibition efficiencies, calculated from weight loss measurements, show the same trend as those obtained from electrochemical studies. Also, the inhibition efficiency was found to increase with increase of the inhibitor concentrations to reach 87.84 % at 10-3M of (OT) due to the adsorption of the inhibitor molecules on the metal surface and the adsorption follows Langmuir’s adsorption isotherm. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. To elaborate the mechanism of corrosion inhibition, the kinetic and thermodynamic parameters for Carbon steel corrosion and inhibitor adsorption, respectively were determined and discussed. Double layer capacitance and charge transfer resistance values were derived from Nyquist plots obtained from impedance studies.