ClO_(2)^(-)对S2205不锈钢在Cl^(-)介质中点蚀初期行为的影响  

Effect of ClO_(2)^(-)on Pitting Initiation of S2205 Stainless Steel in Cl^(-) Containing Medium

作　　者：杨众魁 史艳华[1] 乔忠立 梁平[1] 王玲[1] YANG Zhongkui;SHI Yanhua;QIAO Zhongli;LIANG Ping;WANG Ling(School of Mechanical Engineering,Liaoning Petrochemical University,Fushun 113001,China)

机构地区：[1]辽宁石油化工大学机械工程学院,抚顺113001

出　　处：《中国腐蚀与防护学报》2021年第4期523-528,共6页Journal of Chinese Society For Corrosion and Protection

基　　金：辽宁省教育厅科研项目(L2013154)。

摘　　要：采用金相显微镜观察了脱硝工况下腐蚀失效管件的夹杂物和蚀坑形貌,利用慢速动电位扫描的方法研究了不同浓度ClO_(2)^(-)对S2205不锈钢在含Cl^(-)介质中的亚稳态点蚀的影响。结果表明,一方面ClO_(2)^(-)与O2竞争吸附阻碍钝化膜的生成与修复,强氧化性致使钝化膜部分溶解,稳定性降低;另一方面ClO_(2)^(-)与Cl^(-)竞争吸附,浓度越大置换率越高,一定程度上又保护了钝化膜。ClO_(2)^(-)的引入,ClO_(2)^(-)与Cl^(-)竞争吸附抑制了亚稳态点蚀形核,此时形核以金属表面的夹杂物以及具有一定临界深度的表面沟槽产生活性点诱发为主。由于钝化膜稳定性的降低,浓度增大亚稳态点蚀形核数目稍有上升,亚稳态点蚀生长速率与浓度变化关系不大。添加ClO_(2)^(-)后,Cl^(-)诱发亚稳态点蚀形核受到抑制,E_(m)迅速增大后随浓度变化不明显,钝化膜稳定性降低,E_(b)迅速减小后随浓度增加缓慢减小,亚稳态更容易转变为稳态点蚀。电位升高金属表面夹杂物溶解,抑制了亚稳态点蚀形核,同时增大了Cl^(-)迁移速率,促进了亚稳态点蚀的生长。The effect of ClO_(2)^(-) amount on the metastable pitting of S2205 stainless steel in Cl^(-) containing medium was studied by means of slow potentiodynamic scan.The results show that the competitive adsorption of ClO_(2)^(-) and O_(2)hinders the formation and repairation of the passivation film,while the strong oxidation causes the partial dissolution of the passivation film,thereby its stability is reduced.Meanwhile,ClO_(2)^(-) competes with Cl^(-) for adsorption,the greater the concentration,the higher the replacement rate,as a result,such competition may provide protectiveness for the passivation film to a certain extent.The competitive adsorption of ClO_(2)^(-) and Cl^(-) can suppress the metastable pitting nucleation,at this time,the nucleation could mainly occur on inclusions and active sites on the metal surface,of which the later might be generated on the surface grooves with a certain critical depth.Due to the decrease in the stability of the passivation film,as the concentration of ClO_(2)^(-) increases,the number of metastable pitting nucleation increases slightly,and the growth rate of metastable pitting has little relationship with the concentration of ClO_(2)^(-) .After the addition of ClO_(2)^(-) ,Cl^(-) induced metastable pitting nucleation was inhibited,Em increases rapidly,then its change with the concentration is not obvious,and the stability of the passivation film decreases,caused Eb decreases rapidly,it slowly decreases with the increasing concentration of ClO_(2)^(-) ,then the metastable state of pitting is more likely to be transformed into the stable stage.The increase in potential could facilitate the dissolution of inclusions on the metal surface,inhibiting the metastable pitting nucleation,while increasing the Cl^(-) migration rate and thus promoting the growth of metastable pitting.

关 键 词：S2205不锈钢 ClO_(2)^(-) 亚稳态点蚀 形核 生长 

分 类 号：TG172.5[金属学及工艺—金属表面处理]