Hydrolysis Of Imidazoline Corroson Inhibitors And Their Diffusion Behaviors In Simulated Sediment Layers

C02 corrosion is widespread during oil exploitation,which can not only causes economic losses but also endangers personal safety.Imidazoline is widely used as an ideal corrosion inhibitor.However,imidazoline corrosion inhibitors are not stable in aqueous solution.Imidazoline will be hydrolyzed gradually into amides,which reduces its corrosion inhibition.In addition,in the production,collection,transportation and processing of oil and gas fields,the sediment layer often generates on the surface of the equipment and piplelines.The presence of sediment layer not only causes serious localized corrosion but also hinders the transfer of corrosion inhibitor to the metal matrix.Therefore,whether or not the corrosion inhibitor can diffuse through the deposition layer and inhibit the corrosion is a matter of concern to everyone.The corrosion inhibitor can only play a good role in inhibiting the metal matrix by diffusing through the sediment layer and reaching to the metal matrix.Therefore,the methods of electrochemical impendance spectroscopy(EIS),electrochemical potentiodynamic polarization,IR spectroscopy,quantum chemical calculation,UV-Vis method,SEM,Mercury intrusion experiment and surface tension test have been used to compare the corrosion inhibition of imidazoline and amide,investigate the hydrolysis of imidazoline corrosion inhibitor and study the diffusion behiviors of imidazoline corrosion inhibitors in simulated sediment layers.The main research results are listed as follows:1.Imidazoline corrosion inhibitor and intermediate amides were synthesized at different temperatures and characterized using the method of IR spectroscopy.The corrosion inhibition of them were compared by electrochemical methods.The mechanism of them were studied using the method of quantum chemical calculation.The EIS and polarization curves show that the corrosion inhibition of imidazoline is better than amide in 3.5wt.%NaCl solution with CO2 saturated.Quantum chemical calculation theoretically illustrate the adsorption properties and the mechanism of action with metal of imidazoline and amide molecules.The results show that imidazoline molecules have stronger bonding ability,have stronger ability to attract electrons and have stronger interaction with iron than amide molecules.2.The UV-Vis method was used to study the hydrolysis of imidazoline corrosion inhibitor at different temperatures,pH and concentrations.The temperature,pH of the medium and the concentration of the imidazoline corrosion inhibitor in the solution affect the hydrolysis rate and degree of the corrosion inhibitor to some extent.With the increase of temperature,the hydrolysis rate of imidazoline inhibitor increased,and the degree of hydrolysis increased accordingly.The hydrolysis process of the imidazoline corrosion inhibitor was inhibited in the acidic medium and it was promoted in the alkaline medium.As the pH value of the medium increased,the degree of the hydrolysis increased accordingly.With the decrease of the imidazoline corrosion inhibitor,the hydrolysis was accelerated.But the concentration was found to have no effect on the degree of hydrolysis.3.An experimental device was designed to simulate the diffusion of the corrosion inhibitors.The diffusion behaviors of three different imidazoline corrosion inhibitors with different water solubility were investigated in simulated sediment layer by UV-Vis method,potentiodynamic polarization,SEM and Mercury intrusion experiment.The experimental results show that the diffusion behavior of the corrosion inhibitor in the aqueous solution is related to the water solubility of the corrosion inhibitor.The better the water solubility,the stronger the diffusion ability of the corrosion inhibitor.The SEM results show that the sediment layer obtained in this experiment is relatively dense with no large pores,so it can be used as a simulated sediment layer to study the diffusion of corrosion inhibitor.The analysis of the pore size of the simulated sediment layer by the mercury intrusion experiment showed that the pore size of the sediment layer was mainly distributed in the range of 7-20μm before the experiment,and the pore size of the sediment layer was mainly distributed in the range of 10-100 μm after the experiment.The result demonstrates that the pore size of the sediment layer becomes larger after 15 days of immersion and infiltration of corrosion inhibitors.4.The surface tension of three kinds of imidazoline corrosion inhibitors was tested by surface tension meter at different concentrations,and the critical micelle concentration of three inhibitors in 3.5wt.%NaCl solution at 25℃was obtained.The experiment found that the critical micelle concentration of three kinds of corrosion inhibitors from low to high meet the conditions:SOIMS<SOIM<OIM.Since the corrosion inhibition rate of the corrosion inhibitor near.the critical micelle concentration is the highest,the concentration required for the highest corrosion inhibition rate of the SOIMS corrosion inhibitor is the lowest,and the concentration required for the OIM corrosion inhibitor to achieve the highest corrosion inhibition rate is the highest,and the SOIM corrosion inhibitor is somewhere in between.