Corrosion And Protection Research Of Anode Titanium Of Chlor-alkali Electrolytic Ceii

The chlor-alkali industry is the basic chemical industry,and the safety and environmental protection of the chlor-alkali production process contributes to the stable development of the chlor-alkali industry.However,as the core equipment of chlor-alkali production,the ion membrane electrolytic cell is in a complex corrosive environment during production,and its corrosion problems have been reported from time to time.The research work in this thesis based on the corrosion leakage problem of anode titanium plate of ion membrane electrolytic cell in a chlor-alkali plant.Corrosion regularity of industrial pure titanium TA2 was studied respectively in acidic high concentration sodium chloride solution,lmol/L NaOH solution with different Cl-concentrations,and NaOH solution with different temperature and mass concentrations through corrosion electrochemical testing technology and surface morphology analysis.In addition,the self-designed flow corrosion test device was used to study the corrosion electrochemical behavior of TA2 under flowing conditions.The main conclusions are as follows:(1)The corrosion of TA2 in acidic high-concentration sodium chloride solution is affected by the synergy of Cl-concentration,temperature and pH value.The effect on the corrosion current density of TA2 is:PH value>temperature>Cl-concentration.The effect on the hydrogen evolution corrosion rate of TA2 cathode is:PH value>Cl-concentration>temperature.The effect on the self-corrosion potential of TA2 is:PH value>Cl-concentration>temperature.The effect on the TA2 charge transfer resistance is:PH value>Cl-concentration>temperature.and there is a clear corrosion perforation phenomenon.The effect of pH on TA2 corrosion is dominant.(2)When TA2 is in 1mol/L NaOH solution with different Cl-concentrations,the anode polarization curve obviously has passivation zone,and TA2 still has good corrosion resistance with the increase of Cl-concentration.The cathodic hydrogen evolution potential of TA2 in solution is about-1250mV,and Cl-concentration has little effect on hydrogen evolution reaction in potential range of-1600～-1250mV.And when the potential rises,Oxygen absorption corrosion will occur on TA2 surface between-1250～-400mV.With the increase of Cl-concentration,the current density of oxygen absorption corrosion increases first and then decreases.The passivation film of TA2 in solution is n-type semiconductor,which has strong corrosion resistance to Cl-.(3)When TA2 is in the different temperature and mass concentrations of NaOH solution,the corrosion increases with the increase of temperature and mass concentrations of NaOH solution.And,the larger the mass concentrations of NaOH solution is,the more obvious the effect of temperature on the corrosion current density is.Similarly,the higher the temperature of the solution is,the more obvious the influence of the mass concentrations of the NaOH solution on the corrosion current density becomes.Through the analysis of the results of TA2 immersion test in NaOH solution,it can be obtained that the corrosion kinetics curve of TA2 in NaOH solution is weight gain when the NaOH mass concentrations is ≤20%at 35℃,60℃,85℃ and the corrosion curve consists of three parts at 85℃.In the first parts(0-10days),as the corrosion time increases,the corrosion weight increases slowly;in the second parts(10-20days),the corrosion weight increased rapidly;however,in the third parts(20 to 25 days),the corrosion weight increased slowly again.(4)When TA2 is in flowing NaOH solution,both its charge transfer resistance and membrane resistance reduce,the passive film on TA2 surface becomes thin,and the corrosion increases with the increase of the mass concentrations,temperature and flow rate.