关键词: 缝隙腐蚀, 印刷线路板, 阵列电极, Cl-, pH

Abstract: Although the crevice corrosion of metals had been extensively studied in the past years,it remained lack of direct experimental information of the micro chemical environments and electrochemical conditions inside the corroding crevice.The distribution of chloride concentration and local pH in the occluded area are the most crucial factors in development of crevice corrosion.The array probes in one dimension of Ag/AgCl and IrO2 array were developed in this work to in situ follow the distribution of chloride concentration and local pH in the occluded area during the crevice corrosion propagation.Based on a designed simulated crevice corrosion system in 0.5mol/L NaCl solution,the distribution of chloride concentration and local pH for the electronic circuit board inside corroding crevice were imaged correlated with corrosion potential in the crevice.It is found that the chloride concentration increases and the local pH decreases inside the corroding crevice with the immersion time.And the Cl-concentration and local pH at the deeper location inside the crevice are always higher and lower,respectively,than that near the mouth of crevice,due to the mass transfer difficulty by geometrical limitation of crevice.That is the reason why the crevice corrosion always develops in depth direction.All obtained experimental results provide a further understanding to the mechanism of crevice corrosion of electronic materials in the given environments.

Key words: crevice corrosion, copper electronic board, array electrode, chloridion, pH