不同晶粒尺寸的Cu-40Ni合金在酸性介质中的耐蚀性能

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介质中的腐蚀电化学性能以及腐蚀机理。结果表明:随着H 浓度的增加,CA Cu-40Ni合金的自腐蚀电位负移,而MA Cu-40Ni合金则正移,两种合金的动电位扫描极化曲线均未出现钝化现象;随着H 浓度的增加,CA Cu-40Ni合金的极化电阻增大,腐蚀电流减小,合金的耐蚀性能增加,而MA Cu-40Ni合金的极化电阻减小,腐蚀电流增加,合金的耐蚀性能降低。两种合金的交流阻抗谱均由双容抗弧组成,腐蚀过程受电化学反应控制。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MA Cu-40Ni合金的腐蚀速度高于CA Cu-40Ni合金。

Corrosion behavior of Cu-40Ni alloy with different grain sizes in acidic media

The corrosion mechanism and corrosion-resistances of Cu-40Ni alloy prepared by conventional casting(CA),mechanical alloy(MA) and hot-pressing processes with the great difference in grain size in acidic media were investigated by PARM273A and M5210 electrochemical apparatus through the potentiodynamic polarization method and the electrochemical impedance spectroscopy(EIS) technique.The results show that the corrosion potential of CA Cu-40Ni alloy in acidic medium moves negtively,while MA Cu-40Ni alloy moves positively with the increase of the H~ concentration.There is no passive phenomenon in potentiodynamic polarization curve for the two alloys.With the increase of the H~ concentration,the polarization resistance increases,and the corrosion current decreases,so the corrosion resistance increases for CA Cu-40Ni alloy,while the polarization resistance decreases,and the corrosion current increases,so the corrosion resistance decreases for MA Cu-40Ni alloy.The electrochemical impedance spectroscopy(EIS) composed of double capacitive loops for the two alloys show that the corrosion process is controlled by electrochemical reaction.The corrosion rate of MA Cu-40Ni alloy becomes faster than that of CA Cu-40Ni alloy because the reduction in the grain size of MA Cu-40Ni alloy produces large concentrations of grain boundaries and increases the number of reactive atoms in alloy surface.