Synthesis Of Imidazoline Type Inhibitors And Study On Inhibitory Properties

In recently years the imidazoline type inhibitors have been the focus of research and were used widely in industrial applications (i.e., to remove mill scale in pickling solutions, acidization of oil wells, removal of scale and rust etc.). The imidazoline type inhibitors were friendly to environment, high efficiency and low toxicity. Their syntheses were simple and the materials were easy to get. There are good inhibitors and have high efficiency with low addition in aggressive media.In many references, the imidazoline type inhibitors were synthesized from carboxylic acid and organic amine dehydration that formed a cycle under certain temperature and condition. In this paper, the method of synthesis was improved. Two Schiff-base imidazoline type compounds SMI and SEI were synthesized from benzaldehyde, triethylenetetramine and fatty acid. Their structures were characterized by IR spectrum. Their corrosion inhibitions for N-80 steel in 1 mol/L HCL solution were studied by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves and gravimetric measurements. The corrosion kinetics and the effect of temperature for inhibition efficiency were also investigated. Their adsorptions on the surface of N-80 steel and inhibition mechanism were discussed.The obtained result showed that compound SMI and SEI were good inhibitors and performed pretty inhibiting efficiency for N-80 steel in 1 mol/L HCL solution. When 100mg/L SMI were used, the inhibition efficiency was 84% and the inhibition efficiency increased as the inhibitor concentration increased. We can get high efficiency with addition low concentration of compound SEI. The inhibition efficiency was over 90% with added 10mg/L SEI in the acid media.Potentiodynamic polarization studies showed that compound SMI and SEI inhibited both anode and cathode corrosion reactions. The compound SMI was a cathodic-type corrosion inhibitor, while the compound SEI was an anodic-type inhibitor.The obtained result from electrochemical impedance spectroscopy (EIS) also showed that compound SMI and SEI were good inhibitors and performed pretty inhibiting efficiency for N-80 steel in 1 mol/L HCL solution. The Nyquist plots from the impedance spectroscopy were good semicircles which indicated that the corrosion of N-80 steel in 1 mol/L HCL solution was controlled by transfer charge and the equivalent circuit can be symbolized by R(RC).The calculated values of corrosion efficiency were good agreement with polarization curves and weight loss measurements. The adsorption of SMI on the surface of N-80 steel obeyed the Langmuir absorption isotherm and the values of adsorption energy Ga was calculated to be -1.028 kJ mol-1 .We have studied the relationship between temperature and inhibition efficiency in the temperature range of 30-60℃. The result showed that the inhibition efficiency was decreased with the increased of temperature. It also indicated that compound SEI was physical adsorption on the N-80 steel surface. The values of activation corrosion energy Ea were determined from the slops of plots and are calculated to be 120 and 79 kJ mol-1 in the presence and absence of SEI. The increase of activation corrosion energy Ea proved that the addition of inhibitor restrained the corrosion reaction.Two rosin type imidazoline inhibitors were synthesized from rosin, diethylenetriamine et al. Their corrosion inhibitions for N-80 steel in 1 mol/L HCl solution were studied by weight loss method. Their adsorptions on the surface of N-80 steel and inhibition mechanism were also discussed.The obtained result showed that the rosin type imidazoline compounds CRI and ORI were good inhibitors and performed pretty inhibiting efficiency for N-80 steel in 1 mol/L HCl solution. The inhibiting efficiency can reach over 89% with addition of 0.1% inhibitors. From the research of their adsorptions on the surface of N-80 steel and inhibition mechanism we learned that the rosin type imidazoline is different from castor type imidazoline in chemical structure, but the...