Study On The Effect Of Rare-earth Ce And Heat Treatment On Intergranular Corrosion Of00Cr12

Taking the00Cr12ferritic stainless steel widely used in auto industry as the researchobject. This article studies the effects on the intergranular corrosion behavior of the heattreatment and the rare-earth Ce by means of Cu-CuSO4-16%H2SO4tests, electrochemicalimpedance spectroscopy (EIS), dynamic electrochemical impedance spectrometry (DEIS), andMott-Schottky tests.The microstructure and the morphology and distribution of inclusions for specimens withdifferent cerium adding were observed through optical microscope and SEM. The results showthat specimens without cerium exist long strip inclusions in the grain boundary, and theinclusions gradually decreases with the increase of content of rare earth, and inclusions beganto become bigger for the specimens with0.04%cerium; the chromium content is low at grainboundary for the specimens without cerium and0.01%cerium, and along with the increaseof cerium addition content, improving the00Cr12ferritic stainless steel intergranular corrosionresistance. When adding0.06%cerium, cerium content of grain boundary is very high,showing that cerium gathers in grain boundary with the form of rare earth inclusions, whichmakes intergranular corrosion resistance of matrix decrease.A hot acid immersion corrosion test platform for testing stainless steel intergranularcorrosion sensitivity was established independently. And the hot acid immersion corrosion testswere proceeded, and then intergranular corrosion sensitivity of specimens with different heattreatment and different cerium addition was studied through tsai microscopy and SEM.Reactivation processes of00Cr12were studied by DL-EPR method, and the influence onintergranular corrosion sensitivity of specimens with different heat treatment and differentcerium addition by the activation rate criterion. Impedance spectroscopy for differentspecimens was obtained by EIS and DEIS technology. In addition, Mott-Schottky was carried out to analyze semiconductor properties of passivation membrane of specimens for differentheat treatment and cerium addition.The heat treatment condition influences the intergranular corrosion sensitivity of00Cr12.It was found that specimens treated at950℃for2h sensitized but specimens treated at650℃for2h did not and intergranular corrosion sensitivity become higher, as the heat treatmenttemperature increased.Rare-earth cerium could efficiently refine the inclusion, purify grain boundary, and reducethe poor of the chromium in grain boundary, to improve the00Cr12ferritic stainless steelintergranular corrosion resistance. With the increase of cerium content, intergranular corrosionresistance increases, when cerium content higher than0.04%, the corrosion resistance isreduced. Hot acid immersion test and electrochemical test showed that00Cr12ferritic stainlesssteel is the best cerium addition content is0.02%.In conclusion, this paper argues that the modified00Cr12should add0.02%ceriumelement, and the best heat treatment system is the650℃for2h and air cold.