Abstract: A simulated occluded corrosion cell was used to study the changes within corrosion cracks or crevices of Cr 18 Ni 9 Ti austenitic stainless steel in NaCl solution. As anodic currents passed the cell a series of changes took place, the most important of which were pH fall and Cl- migration. It was found that the pH fall was proportional to current density and time of current flowing. Consequently, pH fall was a function of the quantity of electricity passing the occluded anode. The pH in the occluded cell might attain negative value whencurrent density was 3.5mA/cm2 after 168 hrs. Meanwhile the Cl- migration into occluded cell increased the Cl- concentration 18 times as much as original concentration. As a rule, the Cl- migration versus unit anode area was proportional to time of current flowing. A linear relationship existed between Cl-migration in g-equivalents per cm2 of anode area and current density, and also a linear relation existed between Cl- migration per hour and current intensity. Consequently, the number of equivalents of Cl- migration into crack tip was proportional to the quantity of electricity passing it. It was interesting to discover that while each faraday passed almost always 1/2 g-equivalent of Cl-migrated into the occluded cell. This relationship did not change whatever were the concentration of bulk solution (from 0.01N to 5N NaCl), current density, temperature and time. Two empirical formulas regarding to the relationship between pH and Cr3+ concentration or Cl- migration respectively were derived based on the relationships between quantity of electricity passing and other variables found in the present experiments, i. e. PH=-2.60-log[Cr3+] pH=-1.84-log[Cl-]

摘要： 本文系用模拟闭塞电池来研究Cr18Ni9Ti奥氏体不锈钢在NaCl溶液中闭塞区内化学和电化学状态的变化.当电流通过闭塞区时,溶液PH值随时间下降,电流密度愈大下降也愈大,可达负值,电极所通过的电量与溶液PH成函数关系.CI~-在闭塞区内的浓集倍数与时间成直线关系,最高测到浓集达9—10倍.在一定电流密度下,与单位阳极面积相应的Cl~-迁入量与时间成正比.若以电流密度对单位时间、单位阳极面积相应的Cl~-迁入量作图或以电流强度对每小时Cl~-迁入量作图,均得直线关系.闭塞区内每迁入1g-eq·Cl~-,电极上通过电量为一常值,约为2F.这个关系不随电流密度、温度、时间及外部溶液含NaCl的浓度而变化.根据实验数据与上述Cl~-迁入量、金属溶解量和闭塞区通过电量的关系,导出闭塞区溶液PH与Cr~(3+)及Cl~-的克离子数的关系经验公式,如下:PH=-2.60—log[Cr~(3+)]PH=-1.84—log[Cl~-]