Inhibition Effect of Some Benzotriazole Derivatives on Carbon Steel in 1M H2so4 Medium

The inhibition effect of some benzotriazole derivatives (1-hydroxybenzotriazole, 5-chlorobenzotriazole and 3-amino-5-mercapto-1,2,4-triazole) on the corrosion of two carbon steels (OL 37 and OLC 45) in 1M H₂SO₄ was studied potentiostatic and potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and metallurgical microscopy techniques.

The inhibition activity analysis of these organic inhibitors was made by assuming that the mechanism of inhibition by organic molecules is chemisorptions and that the energetic of the corrosion process per se is unaffected by the addition of substituents on the parent compound. We presume that, these organic inhibitors inhibit corrosion of carbon steel by a protective mechanism, forming insoluble iron complexes and repairing the porous oxide layers. The addition of the organic inhibitors led in all the cases to inhibition of the corrosion process. Polarization curves indicate that they are mixed type of inhibitors. The inhibition efficiency was high in all the studied cases. The corrosion parameters obtained from polarization curves and from EIS spectra are in good concordance and point out the inhibitory action of derivatives benzotriazole. The adsorptions of the organic compounds on the carbon steels surface obeyed Langmuir^’s isotherm. The thermodynamic parameters of adsorption enthalpy (ΔH⁰), adsorption free energy (ΔG⁰) and adsorption entropy (ΔS⁰) were calculated. Further characterization using Fourier transform infrared spectroscopy (FT-IR) demonstrates the adsorption of organic inhibitors and the formation of corrosion products on the carbon steels surface. The inhibition process was attributed to the formation of the adsorbed film on the metal surface that protects the metal against corrosive agents. The EIS measurements have confirmed this protection and pointed out the formation of adsorption layers on the electrode surface.