某20#钢腐蚀穿孔失效原因分析

目的 某船20#钢管投运不久后管段出现严重的腐蚀穿孔，通过对失效管段进行研究，以分析其失效原因。方法 通过电感耦合等离子体发射光谱仪、碳硫分析仪、金相显微镜等对材料材质进行材质符合性分析及金相组织分析。通过场发射扫描电子显微镜观察蚀坑微观形貌，并结合X射线衍射仪及显微拉曼光谱仪，对失效部位周围的腐蚀产物进行成分分析。通过电化学测试及微生物鉴别培养，进一步确定腐蚀的发生原因及机理。结果 材料符合性分析说明，此20#钢管束成分符合标准要求。通过形貌观察发现，20#钢蚀坑边缘呈阶梯状，具有明显的攀爬现象，蚀坑周围呈黑色。X射线能谱仪分析结果表明，20#钢腐蚀穿孔处内表面异常存在大量硫元素。通过拉曼分析及XRD分析发现，硫元素主要以硫酸盐及硫化物的形式存在。电化学测试结果表明，在含硫化物的溶液中，20#钢的腐蚀速率明显提升。进一步对腐蚀产物进行微生物培养，发现了硫酸盐还原菌的存在。结论 微生物腐蚀是引起20#钢管束穿孔的主要原因。

Failure Cause of Corrosion Perforation of a Certain type 20# Steel

The work aims to analyze the cause of the failure by studying the failure section of the 20# steel pipe of a certain vessel after it is put into operation. The compliance and metallographic structure of materials were analyzed with an inductively coupled plasma emission spectrometer, a carbon and sulfur analyzer and a metallographic microscope. A field emission scanning electron microscopy (SEM) was used to observe the microscopic morphology of the corrosion pits, and the composition analysis of the corrosion products around the failure sites was carried out by X-ray diffraction and microscopic Raman spectroscopy. The causes and mechanism of corrosion were further determined by electrochemical test and microbial identification culture. The analysis of material compliance showed that the composition of the 20# steel pipe beam met the requirements of the standard. It was found in morphological observation that the edge of the 20# steel pit was stepped, with obvious climbing phenomenon, and the pit was black around. The results of X-ray energy spectrometer showed that there was a large amount of sulfur on the inner surface of 20# steel, and it was found by Raman analysis and XRD analysis that sulfur elements mainly existed in the form of sulfate and sulfide. The electrochemical test results showed that the corrosion rate of 20# steel was increased obviously in the solution containing sulfide. Further microbial culture of the corrosion products revealed the presence of sulfate reducing bacteria. Therefore, microbial corrosion is the main cause of perforation of 20# steel pipe.