Research On Inhibition Performance Of Quinoline On X70 Steel Base And Weld

Water flooding is a new way to increase oil production.As the water contains high salinity and there exists abundant H2S around the oil well,these mix water media may corrode the water flooding badly,which has serious effect on oil mining and the working life of oil devices.The injection water with corrosion inhibitors can effectively prevent the oil devices from corrosion.Especially when the pipeline surface forms passive film,the film can alleviate the injection water corrosion.But the film forming mechanism of quinoline inhibitor on steel surface has not been known;the dynamics of forming film has not been reported.Especially the research on the recovery performance of the formed film which was damaged during operating process limited to theoretical analysis,Which greatly restricted the application and intensive study of quinoline inhibitor.In this paper,the corrosion inhibition and mechanism of quinoline on X70 steel base and weld in simulated injection water were investigated using weight-loss method,electrochemical methods such as potentiodynamic scanning method,Electrochemical Impedance Spectroscopy(EIS).The adsorption model of quinoline was discussed.Rapid scratching electrodes technique combined with math simulation and high field iron conduction model was used to study the reaction process and growing dynamics rules of the inhibitor film forming on X70 steel base and weld surface.The results showed that quinoline was able to inhibit the corrosion of X70 steel base and weld in injection water.The adsorption process of quinoline on X70 steel base and weld both belonged to adsorption film forming mechanism.The process obeyed Langmuir isothermal adsorption model and temperature went against the adsorption of quinoline on steel surface.The polarization curves of X70 steel base and weld both moved down after adding quinoline.The corrosion current density decreased and corrosion potential became more positive.The anode polarization curves of steel base and weld showed obvious passivation because of forming adsorption film.The impedance spectra of X70 steel base and weld both consisted of capacitive arc in high frequency region and diffusion tail in low frequency region.Corrosion process met the circuit model of Rs(CPE(RctW0)).The changes of quinoline concentration and test temperature only changed charge transfer resistance and capacitance values,but the corrosion model kept the same.After the addition of quinoline,charge transfer resistance Rct of X70 steel base and weld increased and capacitance Cdl decreased,but diffusion index n didn't change apparently.At 25?,at the quinoline concentration of 1.2wt.%,the current density after scratching could decay to that before scratching in around 100s.Once the specimen was damaged,the surface of steel base and weld could rapidly form adsorption film.Growing dynamics rules of the inhibitor film forming on X70 steel base and weld surface followed i(t)=Imaxexp(-?t),where ? characterized grow rate of adsorption film,Imax showed peak current density.Grow rate constant ? increased with the increase of quinoline concentration and reduced with the increase of temperature.The grow mechanism of adsorption film obeyed high field iron conduction model.