低碳钢中小孔形成及腐蚀原因的模拟对比研究

Comparative Simulation Study of the Pore Formation and Corrosion of Low Carbon Steel Pipeline

外涂沥青的埋地低碳钢汽油输油管使用8a之后,出现了穿孔,造成了比较大的经济损失。为此,通过金相、扫描电镜、能谱和X射线衍射等手段对合金的断口、微观组织、微区成分和断口表面覆盖物相组成进行了分析。分析发现,孔边沿的金相组织中未发现变形层,孔口处的残留产物主要为尖晶石类氧化物Fe3O4,该氧化物为大气下形成的氧化物,未发现FeO等高温氧化产物,分析结果排除了人为破坏穿孔的可能。研究结果表明,油管穿孔是一种典型的局部腐蚀,其主要腐蚀机理为闭孔形式的小孔腐蚀。大阴极和小阳极进一步加速了这种腐蚀过程。

Simulation comparative study on the hole penetration in a low carbon pipeline was conducted. Optical metallography, scanning e-lectronic microscope, energy spectrum analysis and X-ray diffrac-tion were used in the investigation of the fracture, microstructure, chemical composition and phases in the alloy. The possibility of arbitrary penetration of the steel pipeline was excluded by micro-structure analysis and phases detective technique. The hole in the pipeline was generated by localized corrosion. The major mechanism in this failure case was occluded cavity corrosion. In the corrosion process, the corrosion was accelerated by a high cathode to anode area ratio.