温度和pH值对20~#钢盐酸露点腐蚀行为的影响

Effect of temperatures and pH values on the hydrochloric dew point corrosion behavior of 20~# steel

针对常压塔顶系统出现的盐酸露点腐蚀,利用失重法、扫描电子显微镜（SEM）、能谱仪（EDS）和X射线衍射（XRD）等分析手段,对不同温度、不同p H值下20#钢的盐酸露点腐蚀速率、腐蚀形貌及腐蚀产物进行了分析.结果表明：随温度的增加,20#钢的盐酸露点腐蚀速率呈先增加后减小的趋势,在90℃时达到峰值;20#钢的盐酸露点腐蚀速率与HCl溶液p H值负相关,随HCl溶液p H值的增加,露点腐蚀速率快速降低;20#钢表面整体为均匀腐蚀,局部区域伴有腐蚀坑,温度高于90℃时,随温度的升高腐蚀坑数量增多;随p H值增大,腐蚀坑数量减少且腐蚀坑变浅,溶液中存在的氯离子（Cl-）会加深腐蚀坑,加速腐蚀;X射线衍射分析表明：20#钢表面腐蚀产物膜的主要成分为α-Fe OOH、Fe3O4和γ-Fe OOH.

Hydrogen dew point corrosion often occurs in the overhead condensing and cooling system of an atmospheric distillation unit at the initial process of petroleum refining because of the formation of a highly suitable corrosive environment.The consequent thinning and leakage of equipment cause serious environmental pollution and endanger personal safety.Hydrochloric dew point corrosion is affected by various factors,among which temperature and p H values are the most critical.In this study,the hydrochloric dew point corrosion behavior of the 20#steel of an atmospheric tower overhead system as well as its corrosion rate,corrosion morphology,and corrosion products at different temperatures and p H values were analyzed by some analytical methods,such as weight loss method,scanning electron microscopy（SEM）,energy dispersive spectrometer（EDS）,and X-ray diffraction（XRD）.The results indicate that the hydrochloric dew point corrosion rate of the 20#steel first increases and then decreases with temperature increase,and reaches its peak at 90℃.The hydrochloric acid dew point corrosion rate of the 20#steel is negatively correlated with the p H values of HCl solution,and the dew point corrosion rate decreases rapidly with an increase of the p H value of HCl solution.Generally,uniform corrosion occurs on the steel surface accompanied with local corrosion pits.When the temperature is higher than 90℃,the number of corrosion pits increases with temperature.The corrosion pits become shallower and decreases with an increase of p H value.In addition,the chloride ions in the solution deepen the pits and accelerate the corrosion.The XRD analysis shows that the main compositions of the corrosion products areα-Fe OOH,Fe3O4,andγ-Fe OOH.