钨酸根对不锈钢局部腐蚀的作用

采用模拟闭塞电池恒电流实验研究了304不锈钢在0.5(mol·L^-1)NaCl(pH=7)溶液中及添加不同浓度钨酸钠后局部腐蚀闭塞区内化学状态的变化。结果表明,主体溶液中添加一定浓度的WO₄^2-离子后,随着时间的延长,闭塞区的pH值下降明显减缓,Cl^-离子浓集倍数降低。WO₄^2-离子与Cl^-离子向闭塞区内竞争迁移。当添加的WO₄^2-离子浓度较低时,Cl^-离子的电迁移量仍然随时间的延长而增加;WO₄^2-离子浓度达到一定值后,WO₄^2-离子能有效地阻止Cl^-离子向闭塞区的迁移,钨酸根浓度越高效果越显著。闭塞区内WO₄^2-离子浓度随主体溶液中WO₄^2-离子浓度的增加而增大。对一定浓度WO₄^2-的主体溶液,WO₄^2-离子向闭塞区的迁移量随时间延长而增大,迁移速率则随时间的延长而降低。

A study on the mechanism of localized corrosionof stainless steel by tungstate

Simulated Occluded Corrosion Cell(OCC) was used to study the changes of chemical state within the OCC of 304 stainless steel in neutral solution of 0.5 mol/L NaCl containing various tungstate ion concentration at 50 ℃. Anodic polarizing occluded specimen to simulate reaction current between outside and inside of OCC. It was found that when WO2-4 anion was added into the bulk solution, it migrated into OCC, and the migration quantity increased with the concentration and the time,the migration rate decreased with the time. WO2-4 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 is. WO2-4 can retard pH fall and decrease the multiples of Cl- enrichment effectively.