氮气保护下炼化企业停工装置的腐蚀行为研究

RESEARCH ON CORROSION BEHAVIOR OF SHUTDOWN EQUIPMENT OF REFINING AND PETROCHEMICAL PLANT UNDER NITROGEN PROTECTION ATMOSPHERE

模拟停工装置内潮湿环境,对20号钢、16MnR、Cr5Mo和304不锈钢等4种典型材质,在氮气置换保护条件下的腐蚀进行试验,考察了氧含量对4种材质腐蚀的影响。利用挂片失重法、3D轮廓仪和XRD等手段对试样进行了腐蚀速率分析、腐蚀形貌观察和腐蚀产物组成分析。结果表明:气相潮湿环境下,随着氧含量的增加,碳钢腐蚀速率先降低后平稳增加,Cr5Mo和304不锈钢的腐蚀速率均稳定保持在较低的水平;液相环境下,当氧体积分数大于1.0%时碳钢和铬钼钢腐蚀速率有升高的趋势;氧体积分数为0.5%~1.0%时各材质在气液两种环境下的腐蚀速率相差不大;碳钢和铬钼钢的宏观形貌基本一致,腐蚀产物主要是疏松的γ-FeOOH和致密的Fe3O4,金属基体腐蚀表现为蚀坑和溃疡状腐蚀;304不锈钢未见明显腐蚀,仍保持金属光泽。选取某企业停工装置的典型部位进行了周期114天的现场挂片试验,结果表明,在氧体积分数为0.5%的情况下,各部位的停工保护效果良好。

The oxygen corrosion behaviors of No.20,16 MnR,Cr5 Mo,and 304 steel in nitrogen protection were studied under the simulated wet environment.The corrosion rate,corrosion appearance and the composition of corrosion products were investigated by coupon weight-loss method,3 Dprofilometry and X-Ray（XRD）,respectively.The results showed that,in the humid gas atmosphere,the trend of corrosion rate for carbon steel is to rise first followed by a steady increase with increasing oxygen content;the corrosion rates of Cr5Mo and 304 stainless steels both are stable at a low level.In the liquid phase,the corrosion rates of carbon steel and chromium-molybdenum steel increase obviously when oxygen content reaches to 1.0%.There is small difference of material corrosion rates when the oxygen content changes in the range of 0.5%-1.0% either in gas or liquid phase.The corrosion characteristics of carbon steel and chromium-molybdenum steel are basically the same.The corrosion products mainly consist of looseγ-FeOOH and tight Fe3O4,with metal ulcerated and etched.The 304 stainless steel still maintains the metallic luster and has no obvious corrosion.Typical sites of shutdown equipment were selected to do a corrosion test for 114 d,and the protective effect is fine in the environment with 0.5% oxygen content.