Electrochemical Investigation of Tetranitro Cobalt Phthalocyanine on Corrosion Control of Mild Steel in Hydrochloric Acid Medium

Abstract: Tetranitro cobalt phthalocyanine (TNCoPc) was used as a corrosion inhibition of mild steel in a 0.25 M hydrochloric acid medium using Tafel polarization and electrochemical impedance spectroscopy in a temperature range of 303 to 323 K. The concentration of inhibitor used was in the range of 1.25–5 mM. The surface morphology was studied using scanning electron microscopy, atomic force microscopy, and energy dispersive X-ray analysis. Inhibition efficiency was found to increase with increasing inhibitor concentration and decreasing temperature. Polarization studies revealed that TNCoPc acts as a mixed type inhibitor at all concentrations of it. The maximum inhibition efficiency of 86.48% was obtained with TNCoPc at its optimum concentration of 5 mM. Adsorption studies revealed that the adsorption of this inhibitor underwent both physisorption and chemisorption on the surface of the metal and followed the Langmuir adsorption isotherm. The kinetic and thermodynamic parameters were calculated and discussed in detail. The results obtained by both Tafel polarization and electrochemical impedance spectroscopy methods were in good agreement with each other. TNCoPc emerged as a potential inhibitor for the corrosion control of mild steel in a hydrochloric acid medium.