0Cr15Ni5Cu3Nb Stainless Steel In Cl ~ - Pitting Behavior And Protective Medium

Chemical immersion method and electrochemical impedance technique, this paper studies the0Cr15Ni5Cu3Nb stainless steel in solution containing Cl" medium neutral corrosion behavior. On the basis of preliminary demonstration and test the0Cr15Ni5Cu3Nb6kinds of steel heat treatment process is determined. Using potentiodynamic polarization and cyclic sample of different heat treatment states Cl" pitting resistance was analyzed. Using SEM, EDS and XRD analysis of the microstructure and composition, and various organizations on the corrosion resistance after heat treatment are discussed in this paper. The influence of Chemical immersion test shows that after soaking wafer sample for macroscopic observation,6set sample are a little cavitation. Corrosion rate was calculated by the weight loss method,12h corrosion rate is very fast, but after72h, corrosion rate is leveling off, the corrosion rate is nearly four times. At the beginning of the pitting because Cl" concentration produces poor Cr area and uneven easily dissolved passivation membrane formation, in the center of the erosion hole edge will generate a new activation, new nuclear generation accelerates the iron substrate loss, also is the main reason for the initial corrosion rate is faster.0cr15ni5cu3nb corrosion of stainless steel based on Cl" environment, in the early stage is the focus of the protection. To avoid Cl" concentration, prevent to produce new activation center, speeds up the valve or piping containing Cl" liquid medium.Directly after solid solution aging due to C and Cr form Cr23C6phase, resulting in poor Cr area. Pitting nuclear priorities in the lean Cr23C6form around. Compared with the untreated sample, pitting corrosion resistance decrease. And adjust the processing after0Cr15Ni5Cu3Nb stainless steel Nb and C is preferred to generate Nb C phase in the organization, reduce Cr23C6phase formation, and makes the martensite structure small features, could improve the ability of resistance to pitting of Cl-. To adjust processing, with the increase of adjusting temperature, the precipitation of Nb C less gradually, increase the poverty degree of Cr in the region, there will be a small amount of lean Cr area, thus the corrosion resistance and reduced. Because when adjust the processing temperature, the solubility of Nb is reduced, the inhibitory effect on the phenomenon of poverty is Cr in steel decreases, thus resistance to pitting corrosion performance degradation. Eventually determine0Cr15Ni5Cu3Nb martensitic precipitation hardening stainless steel resistant to Cl" pitting the best heat treatment process is a solid solution (1050℃+1h, water-cooled)+adjustment (815℃(0.5h)+time (520℃by4h, air cooling).