Anti-corrosion Properties of some Triphenylimidazole Substituted Compounds in Corrosion Inhibition of Carbon Steel in 1.0 M Hydrochloric Acid Solution

Two triphenylimidazole substituted compounds, namely 2,4,5-triphenyl-4,5dihydro-1H-imidazole (P1) and 2-(4,5-diphenyl-4,5-dihydro-1H-imidazol-2-yl)phenol (P2) were studied as inhibitors for the corrosion of carbon steel in 1.0 M hydrochloric acid (HCl) solution has been examined and characterized by weight loss, Tafel polarization and electrochemical impedance spectroscopy (EIS). It was found that the studied compounds exhibit a very good performance as inhibitors for carbon steel corrosion in 1.0 M HCl. Results show that the inhibition efficiency increases with decreasing temperature and increasing concentration of inhibitors. Good agreement between the results obtained from weight loss and electrochemical measurements. It has been determined that the adsorption for the studied inhibitors on carbon steel complies with the Langmuir adsorption isotherm at all studied temperatures. The kinetic and thermodynamic parameters for carbon steel corrosion and inhibitor adsorption, respectively, were determined and discussed. On the bases of thermodynamic adsorption parameters, comprehensive adsorption (physisorption and chemisorption) for the studied inhibitors on mild steel surface was suggested. Results show that the order of inhibition efficiency is P2>P1 due to presence of electron donating hydroxyl (−OH) groups in P2. Potentiodynamic polarization studies have shown that compounds studies acts as a mixed type of inhibitor’s. Scanning electron microscopy (SEM) was performed and discussed for surface study of uninhibited and inhibited carbon steel samples.