摘要
热钾碱脱碳液 30 4不锈钢管束再沸器投用 2年后发生了腐蚀泄漏 ,检查发现腐蚀发生在管子与管板之间的缝隙中 .用电化学方法和能谱分析技术 ,对 30 4不锈钢换热管及 1 6Mn管板在热钾碱脱碳液中的极化行为及管子表面腐蚀区的腐蚀产物进行了分析 ,结果表明 :换热器管束的腐蚀是由于缝隙内外五价钒浓差造成的 1 6Mn管板的活化—钝化短路电池所引起 ,缝隙内闭塞电池的形成加速了缝隙内 1 6Mn的溶解速度 ,并使缝隙内介质酸化及Cl-等阴离子富集 ,导致 30
304SS heat exchanger tubes,which have been used for only two years,suffered from leakage due to corrosion.After examining the failed heat exchanger macroscopically,it was found that corrosion occurred in the crevices between sheet of 16 Mn steel and tubes of 304SS.In this paper polarization behavior of 304SS and 16 Mn was studied by electrochemical method in hot potassium carbonate solution both inside and outside the crevice. Analyses by EDS as well as pH value test were made on the surface of corroded area and uncorroded area.It is concluded that lack of V 5+ in the solution inside crevice between sheet and tubes made the 16 Mn sheet change from passive state to active state, so active passive cells were produced between 16 Mn in passivation and 16Mn in activation. Occluded cells generated inside crevice speeded up solution rate of 16 Mn inside crevice, enabled the medium to be acidated and negative ions such as Cl - to be concentrated.With the decrease of pH value and increase of Cl -,piting corrosion of 304SS occurred. With the decrease of pH value uniform corrosion of 304SS occurred. It is put forward to delay the corrosion that pre passivation of 16Mn and welding should be used in connection of sheet and tubes.
出处
《腐蚀科学与防护技术》
CAS
CSCD
北大核心
2004年第5期337-340,共4页
Corrosion Science and Protection Technology
