Effect of organic corrosion inhibitors functional groups (azo and azomethine) on carbon steel N80 alloy corrosion using the electrochemical polarization technique

This study prepared the azo compound (A) and the Schiff base compound (S) from the same amine compound 3-aminopyridine.The identity of these two prepared compounds was confirmed using several techniques: via FT-IR, UV-vis, 1 H NMR, 13 C NMR, EI-Mass, SEM, and EDS spectroscopic techniques.These two compounds were applied as corrosion inhibitors for carbon steel N80 by taking several molar concentrations: 0.0001; 0.0005; 0.001 and 0.005 M, at different temperatures of 298, 308 and 318 K in an acidic medium of HCl at a concentration of one molar.The technique used in this study is electrochemical polarization (Tafel curves).The results obtained from this study confirmed that the corrosion current is high in the absence of inhibitors but decreases in the presence of inhibitors.Also, the corrosion current is inversely proportional to the increase in concentrations of organic inhibitors and directly proportional to the temperature increase.Besides, the percentage of inhibition efficiency increases with increasing temperature, indicating that the adsorption is chemisorption.We also studied the activation energy, and the following thermodynamic parameters have been calculated from the Langmuir adsorption isotherm: free energy (ΔG 0 ), enthalpy (ΔH 0 ) and entropy change (ΔS 0 ).This electrochemical method (Tafel extrapolation) and SEM and EDS techniques have confirmed that these prepared inhibitors are effective against corrosion through the formation of a protective film on the surface of carbon steel.