液相还原法制备的纳米晶Ag-50Ni合金在含Cl-介质中腐蚀电化学行为研究

用液相还原法制备纳米尺寸Ag-50Ni粉末而后热压制得其纳米块体合金,并与传统粉末冶金法制备的粗晶Ag-50Ni合金对比研究了它们在含Cl-介质中的腐蚀电化学行为.结果表明：合金粉末平均粒径约为45nm，真空热压后，晶粒有所长大，但仍为纳米尺度;随Cl-浓度增加，两种尺寸Ag-50Ni合金的腐蚀电流密度均增加，腐蚀速度加快；晶粒尺寸降低后，腐蚀电流密度略有增加，腐蚀速度变快;当极化电位增到某一程度后，两种尺寸Ag-50Ni合金均出现钝化;纳米尺寸Ag-50Ni合金在含0.02mol/L Cl- 介质中的交流阻抗谱由双容抗弧组成，其余均由单容抗弧组成，腐蚀受电化学反应控制.

ELECTROCHEMICAL CORROSION BEHAVIOR IN CHLORIDE ION CONTAINING MEDIA OF A NANOCRYSTALLINE BULK Ag-50Ni ALLOY

Precursory alloy powders with an average particle size of about 45nm were obtained by aqueous reducing method firstly and then a nanocrystalline Ag-50Ni bulk alloy was prepared through hot pressing the precursor at 620℃ under a pressure of 58 MPa.The grain sizes of the bulk alloy after hot pressing still remained in nano-size range.The electrochemical corrosion behavior of the nano-alloy was compared in chloride ion containing media with the corresponding coarse grained alloy prepared by conventional powder metallurgy.Corrosion current densities of nanocrystalline and coarse grained Ag -50Ni alloys increase and therefore corrosion rates become faster with the increment of chloride ion concentrations.However,the corrosion current densities of nanocrystalline Ag-50Ni are a little bigger than those of the corresponding coarse grained Ag-50Ni.Ag-50Ni alloys showed passivation behavior in media containing chloride ions with increment of polarization potentials.EIS plot of nanocrystalline Ag 50Ni is composed of single capacitive loop in a medium containing 0.05 mol/L Na2SO4 plus 0.02 mol/L NaCl, while the others are composed of double capacitive loops.Thus,corrosion processes are controlled by electrochemical reactions.