晶粒细化对Cu-40Ni合金在酸性含Cl-介质中耐蚀性能的影响

采用电弧熔炼（CA）和机械合金化（MA）通过热压烧结工艺制备了晶粒尺寸差别较大的Cu-40Ni合金，借助于PARM273A和M5210电化学综合测量仪，利用动电位扫描法和交流阻抗技术对比研究了上述合金在酸性含Cl^-介质中的腐蚀电化学性能以及腐蚀机制。结果表明：两种合金的腐蚀电位随时间逐渐稳定，在中性Na2SO4溶液中加入H2SO4和NaCl后，两种合金的自腐蚀电位负移；晶粒细化后，两种合金的自腐蚀电位则正移。两种合金在中性及酸性含Cl^-介质中均存在钝化现象，但在酸性含Cl^-介质中钝化区间很短，钝化能力较弱。两种合金的交流阻抗谱均由单容抗弧组成，反应由电化学过程控制。晶粒细化后，合金中存在大量晶界，参与腐蚀反应的活性原子数增加，促使MACu40Ni合金的腐蚀速度高于CACu-40Ni合金。

Effect of Grain Size on Corrosion Behavior of Cu-40Ni Alloys in Acidic Media Containing Cl-

Corrosion mechanism and corrosion-resistances of Cu-40Ni alloys prepared by conventional casting(CA),mechanical alloy and hot-pressing processes(MA) with the great different grain size in acidic media containing Cl~-were investigated by PARM273A and M5210 electrochemical apparatus through potentiodynamic polarization method and electrochemical impedance spectroscopy(EIS) technique.Results show that the corrosion potential of CACu-40Ni and MACu-40Ni alloys moves negatively when adding H_2SO_4 and NaCl to Na_2SO_4 solution,while the corrosion potential of the two alloys moves positively with the reduction of the grain size.There is passive phenomenon in potentiodynamic polarization curves for the two alloys in Na_2SO_4 media and acidic media containing Cl~-,but range of passivation is very narrow in acidic media containing Cl~-.Corrosion current increases,so corrosion resistance decreases for the two alloys with adding H_2SO_4 and NaCl to Na_2SO_4 solution and the reduction of the grain size.The electrochemical impedance spectroscopy(EIS) of the two alloys in acidic media containing Cl~-is composed of single capacitive loop,therefore corrosion process is controlled by electrochemical reaction.The corrosion rate of MACu-40Ni alloy becomes faster than that of CACu-40Ni alloy because the reduction in the grain size of MACu-40Ni alloy produces large concentrations of grain boundaries and increases the number of reactive atoms over alloy surface.