黄磷罐的失效分析

FAILURE ANALYSIS OF YELLOW PHOSPHORUS TANKS

同一工艺制造的一批黄磷储运罐,在灌装液态黄磷时,其中一个罐壁穿孔泄漏造成火灾,不久,另一黄磷罐也发生泄漏。为确定失效原因,对穿孔的罐壁进行了化学分析、显微镜观察和扫描电镜分析。结果表明,黄磷罐的泄漏是点蚀和缝隙腐蚀的结果,而腐蚀发生在油漆层破裂或机械划伤使金属暴露的局部区域。含磷酸的密封水(pH在1．61～1．83)具有腐蚀性,加速了腐蚀进程。对长期潮湿搁置的黄磷罐,建议在空罐内注满干燥的氮气或处理过的水以防腐蚀。

During the pour of liquid phosphorus in a pouring hall, one of 37 similar low-carbon steel railroad freight tanks designed to transport a yellow phosphorus from a chemical-processing plant to user, that began leaking liguid phosphorus and caught fire. shortly afterwared, the tank on another car began leaking and a comprehensive failure analysis to ascertain the cause of the failure was conducted using chemical analysis, optical and SEM metallographic techniques. It was shown that the tank failed due to pitting and crevice corrosion, which occurred in areas where bare steel had been exposed from both break in the coating and mechanical scratches on the paintedsteel. The presence of aggressive cover water containing phosphoric acid and having a pH of 1.61-1.83 was a factor accelerating attack. During long wet layup periods, the recommended practice is to fill the system with day nitrogen or with treated water to avoid corrosion.