Study On The Reduction Behavior Of 304 Stainless Steel To Se(Ⅳ/Ⅵ) In Simulated Groundwater Environment

In order to study the corrosion mechanism of iron-based materials and the interaction between radionuclides and corrosion products of iron-based materials in a groundwater environment（10 mmol/L Na Cl+2 mmol/L Na HCO₃,"10+2"solution）,the corrosion behavior and mechanism of 304 stainless steel in a simulated groundwater environment were studied by electrochemical experiment and immersion experiment.And reduction deposition of Se（IV/VI）by corrosion products of 304 stainless steel was studied in“10+2”solution.The corrosion products and the corrosion morphology of304 stainless steel samples were analyzed by scanning electron microscopy and energy spectrum analysis,X-ray photoelectron spectroscopy,Raman electron microscopy and inductively coupled plasma mass spectrometry,and other characterization methods.Combined with experimental data and electrochemical experimental parameters to explain the corrosion behavior of 304 stainless steel and its influence on the reduction adsorption and deposition behavior of Se（IV/VI）.The experiment draws the following conclusions:（1）The concentration of ions(Ca²⁺,CO₃^2-,Si O₃^2-)increases,the corrosion products deposited on the surface of 304 stainless steel increase,the corrosion product layer is denser,and the corrosion resistance of the sample is enhanced.With the increase in reaction temperature,the active ion Cl-in the solution has a more substantial effect on the dissolution of passivation film,and the passivation film and corrosion product film on the sample surface is corroded at a faster rate.The effect of ions(Ca²⁺,CO₃^2-,Si O₃^2-)is also enhanced,resulting in a denser layer of corrosion products and a more substantial protective effect on the sample.（2）304 stainless steel in the experimental process through 4 stages.Stage 1:After polishing,the sample generates a single-layer passive film structure in the air;Stage 2:The sample of single-layer passivation film structure generates a double-layer passivation film structure in alkaline"10+2"solution;The third stage:active ion Cl-corrodes and dissolves the passivation film of the sample.The solution reacts with the inner passivation film or even the matrix to generate corrosion products containing Fe（II）oxide and deposit them on the surface of the sample or in the corrosion pit.Stage4:The generated corrosion products reduce the dissolved Se to Fe Se₂.（3）304 stainless steel samples were treated by polarization measurements in different simulated groundwater solutions.The corrosion products deposited on the surface of sample were different,and the amount of reducing Fe（II）compounds in the corrosion products was also different.Fe（II）compounds reduced Se（VI）compounds to Se（IV）compounds in the solution.Then Fe（II）compound reacts with Se（IV）compound,and its reduction rate of dissolved Se in immersion solution was different.When the sample was treated by polarization measurements in"10+2"+20 mmol/L Ca Cl₂ solution,the reduction rates of Se（IV）and Se（VI）were about 40%and 45%,respectively.The reduction rates of Se（IV）and Se（VI）were 60%and 65%,respectively,when the sample was treated by polarization measurements in"10+2"+20 mmol/L Na₂CO₃solution.The reduction rates of Se（IV）and Se（VI）are about 50%and 50%,respectively,when the sample was treated by polarization measurements in"10+2"+20 mmol/L Na₂SiO₃ solution.