纳米晶块体Co-45Ni-10Cr合金在H2SO4溶液中腐蚀电化学行为研究

利用粉末冶金工艺制备常规尺寸（CS）Co-45Ni-10Cr合金粉末，再利用机械合金化法制备纳米尺寸（NS）Co-45Ni-10Cr合金粉末，采用真空热压技术得到相应的块体Co-45Ni-10Cr合金。腐蚀介质选择不同浓度的H2SO4溶液，利用电化学工作站分别测试两种Co-45Ni-10Cr（CS和NS）块体合金的自腐蚀电位、动电位极化曲线和交流阻抗谱，对比研究了它们的腐蚀行为以及晶粒细化对于它们腐蚀行为产生的影响。结果表明：两种Co-45Ni-10Cr（CS和NS）块体合金的自腐蚀电位均随腐蚀介质H2SO4溶液浓度增大而发生负移，腐蚀倾向逐渐加剧，同时腐蚀电流密度均增大，电荷传递电阻相应减小，因此腐蚀速度加快。此外，两种Co-45Ni-10Cr（CS和NS）块体合金的交流阻抗谱均为单一容抗弧，说明腐蚀速率均由电化学过程控制。与Co-45Ni-10Cr（CS）合金相比，Co-45Ni-10Cr（NS）合金的腐蚀速率减慢，这表明纳米化后Co-45Ni-10Cr块体合金的耐腐蚀性能有所提高。

Studies on Electrochemical Corrosion Behavior of Nanocrystalline Bulk Co-45Ni-10Cr Alloy in H2SO4 Solutions

The Co-45Ni-10Cr alloy powder with conventional size (CS) was prepared by powder metallurgy process, and the Co-45Ni-10Cr alloy powder with nanometer size (NS) was prepared by mechanical alloying process. The two alloy powders above were hot pressed into the corresponding bulk Co-45Ni-10Cr alloys. The self-corrosion potentials, potentiodynamic polarization curves and electrochemical impedance spectroscopies (EIS) of the two Co-45Ni-10Cr (CS and NS) alloys were tested by an electrochemical workstation with different concentration H2SO4 solutions as corrosive media. The corrosion behavior of the conventional and nanometer size bulk Co-45Ni-10Cr alloys and the influence of grain refinement on their corrosion properties were studied. The results show that the bigger the concentrations of H2SO4 solutions are, the more negative the self-corrosion potentials of the two Co-45Ni-10Cr (CS and NS) alloys become and thus the greater the corrosion tendencies are. Meanwhile, the bigger the concentrations of H2SO4 solutions are, the bigger the corrosion current densities and the smaller the charge transfer resistances become and thus the higher the corrosion rates are. In addition, EIS all show the corrosion rate is controlled by an electrochemical process because they only have a single capacitance reactance arc. Compared with the Co-45Ni-10Cr (CS) alloy, the corrosion rate of the Co-45Ni-10Cr (NS) alloy slows down. It is very evident that the corrosion resistance of the Co-45Ni-10Cr bulk alloy is improved after nanocrystallinations.