Synthesis Of Imidazoline Phosphate And Study On Inhibitory Performance

In recent years the imidazoline inhibitors have been the focus of research and were used widely in industrial application (i.e.,to remove mill scale in picking solution, acidization of oil wells, removal of scale and rust etc.). The inhibitor preparation methods are simple and easy to get raw materials. They are friendly to environment, lower toxicity. Therefore, they are good inhibitors and have high efficiency with lower addition in aggressive media.Based on the above consideration, the target product imidazoline phosphate was synthesized with alkylimidazoline and 2-hydroxy-3-chloropropyl phosphate sodium, characterized its structure used the infrared spectroscopy, and discussed the optimum conditions of synthesis of alkylimidazoline and the target product. Weight loss method, polarization curves, and electrochemical impedance spectroscopy method were used to investigate the corrosion inhibition performance of Q235 steel in 1mol/L hydrochloric acid solution with the target product and the mixed inhibitor with KI compound; Quantum chemical methods were used to validate the law between the molecular structure and the inhibition performance; Their adsorption models on the Q235 steel and inhibition mechanism were also studied.The weight loss results show that the synthesized imidazoline phosphate salts and mixed compounds perform pretty inhibition efficiency for Q235 steel in 1mol/L hydrochloric acid solution. The inhibition efficiency of these two kinds of corrosion inhibitor increases with the concentration, and the inhibition efficiency was over 95% with added 50mg/L inhibitor in the acid media. The composite inhibitors showed the same inhibition effect with lower concentration, which reduced the costs. The mixed inhibitor had better inhibition efficiency than imidazoline phosphate salts at higher temperature.Polarization curve test results showed these two kinds of corrosion inhibitors both can inhibit the anode and cathode corrosion reaction, had good inhibition performance. The imidazoline phosphate was mixed-controlled inhibitor and the corrosion potential of the system did not shift. The corrosion rate firstly increased then decreased slightly with the time, and the corrosion current density reached the minimum value at 72h. The corrosion potential was negative shift significantly when added the mixed inhibitor to the acid media, the anode and cathode current density was significantly reduced, and the compound inhibitor was mix-type inhibitor which mainly inhibited cathodic process. The corrosion current density gradually decreased to the minimum value at the 120h with the time. The compound inhibitor can maintain a high inhibition efficiency in the longer time compared the single inhibitor.The obtained results from electrochemical impedance spectroscopy(EIS)also showed that two kinds of inhitor were good inhibitors and performed pretty inhibition efficiency in lmol/L hydrochloric acid solution. The Nyquist plots from the impedance spectroscopy were good semicircles which indicated that the corrosion of Q235 steel in lmol/L hydrochloric acid solution was controlled by electrochemical reaction. The adsorption film formed on the metal of the two inhibitor grew firstly then decayed with the time. The mixed inhibitor can restore timely compared the single inhibitor, and can maintain high efficiency of 94.74% at 192h.Quantum chemical calculation results showed that several heteroatoms adsorption center (such as N,O)generally adsorped in a plane; which make for the adsorption centers of inhibitor molecule on the surface of Q235 carbon steel, and play a good inhibition performance. Fukui indices showed that the corrosion inhibitor played a role mainly because of provision of electron to the metal surfaces.In addition, adsorption results show the imidazoline phosphate inhibitors followed Langmuir adsorption isotherm on the Q235 steel.