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在实验室模拟含SO_2体积分数分别为0.4×10~(-6)和1×10~(-6)的污染大气环境,研究20~#碳钢的腐蚀规律。借助金相显微镜(OM)、扫描电镜(SEM)观察表面腐蚀形貌,X射线衍射仪(XRD)分析腐蚀产物成分。结果表明,随SO_2含量增加,碳钢腐蚀加快。在两种大气环境中碳钢腐蚀432 h,前者分为2个阶段,均符合指数增长规律;后者分为3个阶段,分别符合指数增加、线性增加和指数衰减规律。在SO_2含量少的大气环境中,锈层较薄,在SO_2含量多的大气环境中,腐蚀产物层向外生长速度相对较慢,锈层较厚。具有丝状腐蚀特征,丝状腐蚀物在晶界和表面活性点上开始生长,然后沿着晶界和铁素体向内延伸,同时在丝状物上有胞状锈的生成。S主要集中在胞状物上,SO_2含量增加,胞状锈的生长速度加快。
The corrosion of 20 ~ # carbon steel was studied in a simulated atmospheric environment with SO_2 volume fraction of 0.4 × 10 ~ (-6) and 1 × 10 ~ (-6) respectively. The surface corrosion morphology was observed by OM, SEM, and the corrosion products were analyzed by X-ray diffraction (XRD). The results show that with the increase of SO 2 content, the corrosion of carbon steel is accelerated. In the two atmospheric environments, the corrosion rate of carbon steel is 432 h. The former is divided into two stages, both of which are in accordance with the law of exponential growth. The latter is divided into three stages, which meet the exponential increase, linear increase and exponential decay law respectively. In the atmosphere with less SO 2 content, the rust layer is thinner, and in the atmospheric environment with more SO 2 content, the corrosion product layer grows relatively slowly and the rust layer is thicker. With filiform corrosion features, filiform corrosions begin to grow at grain boundaries and surface active sites, then extend inward along the grain boundaries and ferrite, with the formation of cellular rust on the filaments. S mainly concentrated in the cell material, SO 2 content increased, the growth of cellular rust faster.