Study On Corrosion Inhibition Behavior Of Chain Steel In Desulfurization Wastewater Of Thermal Power Plant

In recent years,with the national emphasis on environmental protection,coal-fired power plants are also moving towards to ultra-low emissions.The complex composition of desulfurization wastewater from power plants is highly corrosive,which will cause great corrosion loss to the chain steel of the slag extractor and aqueduct body working in the wastewater condition.In order to prolong the service life of the dregs of desulfurization equipment,increase the service cycle of the chain,and ensure the stable operation of desulfurization equipment for a long time,corrosion inhibitors used for power plant slag dredger and tank material chain steel and Q235 steel in desulfurization wastewater and slag water were studied in this paper.In this paper,the chain steel of the slag extractor and the steel Q235 were used as experiment steel,the mixed solution of desulphurization wastewater and slag water was used as corrosion medium,and different corrosion inhibitors were added to carry out the experiments.The corrosion behavior of the chain steel of the slag extractor and the steel Q235 in desulfurized wastewater in different corrosion inhibitor conditions was investigated by metallographic observation,scanning electron microscope(SEM),corrosion weight loss,electrochemical impedance,polarization curve and other methods.Three possible effective corrosion inhibitors were selected to investigate the corrosion inhibition behavior of the test steel.The results of corrosion tests in desulfurization wastewater and slag water show that the longer the test period,the more corrosion produced,and the corrosion rate reduced.Adding appropriate corrosion inhibitor can obviously slow down the corrosion degree of the test steel and improve its corrosion resistance.Sodium tetraborate,hexamethylenetetramine and triethanolamine can all slow down the corrosion reaction.The best corrosion inhibitor is sodium tetraborate.The corrosion rate decreased by 74.02% during the test period.In the test of electrochemical impedance spectroscopy(EIS),the capacitive reactance arc of sodiumtetraborate inhibitor group was much higher than that of other inhibitor groups.The fitting data of alternating current impedance also show that the polarization resistance became larger after adding sodium tetraborate.In the polarization curve measurement,adding sodium tetraborate obtained the highest corrosion potential and the lowest corrosion current density.The results show that sodium tetraborate can significantly reduce the corrosion of the test steel in desulfurized wastewater solution.The experimental study on the combination of sodium tetraborate and polyoxyethylene(PEO)in a ratio of 1:1 was carried out.Through electrochemical experiments,it was found that the experimental group with corrosion inhibitor played a role in reducing corrosion to different degrees.The corrosion inhibition effect of two inhibitor is better than that of one inhibitor alone.After 25 days of corrosion,the corrosion rate decreased by 82.68% compared to the control group,and the polarization resistance(Rp)increased by 8.67 times compared to the control group.The experimental results show that with the increase of the concentration of sodium tetraborate corrosion inhibitor,the effect of reducing corrosion gradually increased.When the amount of corrosion inhibitor is 15 g/L,the corrosion rate of the test steel is the lowest.In the electrochemical experiments,the maximum polarization resistance(Rp)and the minimum corrosion current density were obtained in the group of corrosion inhibitor dosage of 15 g/L,indicating that the corrosion reaction of the test steel was the most difficult.Under the condition of sodium tetraborate corrosion inhibitor,the corrosion products of chain steel and Q235 steel are mainly iron oxides.The corrosion degree of chain steel is lower than that of steel Q235,and the corrosion products are less,the corrosion resistance is better.