有机阴离子对不锈钢局部腐蚀闭塞区的作用及机理

MECHANISM OF LOCALIZED CORROSION OCC OFSTAINLESS STEEL BY ORGANIC ANION

采用模拟闭塞电池恒电流实验研究了 30 4不锈钢在 0 .5mol·L-1NaCl (pH值 7)溶液中及添加不同浓度十二烷基硫酸钠、十二烷基苯磺酸钠后局部腐蚀闭塞区内化学状态的变化 .为了模拟闭塞区内外间的电偶电流 ,对内试件通入电流进行阳极极化 .结果表明 ,主体溶液中添加一定浓度的C12 H2 5SO-4、C12 H2 5C6H4SO-3 离子后 ,随着时间的延长 ,闭塞区的pH值与未加C12 H2 5SO-4、C12 H2 5C6H4SO-3 离子时的pH值相近 ,总是在其上下浮动 .C12 H2 5SO-4、C12 H2 5C6H4SO-3 离子与Cl-离子向闭塞区内竞争迁移 .只有当添加的C12 H2 5SO4Na、C12 H2 5C6H4SO3 Na超过一定浓度时 ,才能有效地阻止Cl-向闭塞区内的电迁移 ,且C12 H2 5C6H4SO-3 抑制Cl-向闭塞区内的迁移效果比C12 H2 5SO-4好 .闭塞区内C12 H2 5SO-4、C12 H2 5C6H4SO-3 浓度随主体溶液中C12 H2 5SO-4、C12 H2 5C6H4SO-3 离子浓度的增加而增大 .对含一定浓度C12 H2 5SO-4、C12 H2 5C6H4SO-3 的主体溶液 ,C12 H2 5SO-4、C12 H2 5C6H4SO-3 离子向闭塞区的迁移量随时间延长而增大 ,而迁移速率则随时间的延长而降低 .C12 H2 5C6H4SO-3向闭塞区内的电迁移速率及电迁移量比C12 H2 5SO-4向闭塞区内的电迁移速率及电迁移量大 .

Simulated Occluded Corrosion Cell were used to study the changes of chemical state within the OCC of 304 stainless steel in neutral solution of 0.5 mol &middot L-1 NaCl containing various organic ion concentrations at 50°C. Anodic polarizing occluded specimen was used to simulate reaction current between outer and inter of OCC. When organic anion was added into the bulk solution, it migrated into OCC, and the migration quantity increased with concentration and time, while the migration rate decreased with the length of time. Organic anion was in competition with Cl- on migration. It can retard the migration of Cl- effectively above a certain concentration. The higher the concentration, the more efficient it was. Organic anion can not retard pH fall but can fall multiples of Cl- enrichment effectively above a certain concentration. The migration quantity and migration rate of DBSAS were greater than that of SDS.