热浸铝镀层在氯化铵环境中的腐蚀行为研究
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摘要
目的研究改进工艺热浸铝后的炼化加氢换热器管束在不同氯化铵环境下的耐腐蚀性能,并对其耐蚀机理进行分析。方法采用改进的热浸铝工艺对20#钢、15CrMo钢和321不锈钢进行表面处理,利用光学显微镜、X射线衍射仪、扫描电镜和能谱仪对镀层厚度、组织和成分进行分析,采用氯化铵垢下腐蚀实验和高温高压釜模拟工况实验评价热浸铝镀层的耐氯化铵腐蚀性能。结果 20#钢、15CrMo钢和321不锈钢热浸铝层无表面缺陷,热浸镀铝层厚度均≥0.080 mm,镀层结构主要由纯Al层、Fe-Al合金层以及少量的Al_2O_3组成。在潮湿氯化铵条件下,20#钢和15CrMo钢的腐蚀速率均随着温度的升高而明显增大,80℃时的腐蚀速率分别达到21.6mm/a和19.9mm/a;321不锈钢有明显点蚀现象。热浸镀铝后,在相同介质中放置一个月,发现三种试样没有腐蚀现象出现。高温高压釜模拟工况实验后,热浸铝镀层表面同样也没有腐蚀现象发生。结论采用改进工艺获得的20#钢、15CrMo钢和321不锈钢换热器管束热浸铝镀层质量符合国家标准要求,潮湿氯化铵垢下腐蚀实验和高温高压釜模拟工况实验结果证实,热浸铝镀层在氯化铵服役环境下具有良好的防腐性能。
The work aims to study the corrosion resistance of hydrofining heat exchangers tubes after improved hot-dipping aluminum treatment in different ammonium chloride environments, and analyze the corrosion resistance mechanism. 20# steel,15 Cr Mo steel and 321 stainless steel were treated by improved hot-dipping aluminum technology. The thickness, structure and composition of coatings were analyzed by optical microscopy, X-ray diffraction(XRD), scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS). The corrosion resistance in ammonium chloride of hot-dipped aluminum coating was evaluated by corrosion test under wet ammonium chloride and simulated service condition test of high temperature and high pressure autoclave. The obtained hot-dipped aluminum coatings on 20 # steel, 15 CrMo steel and 321 stainless steel had no surface defects, and the thickness were all over 0.080 mm. The coating structure was mainly composed of pure Al layer, Fe-Al alloy layer and a small amount of Al_2O_3. Under the condition of wet ammonium chloride, the corrosion rates of 20# steel and 15 CrMo steel increased obviously with the increasing temperature. The corrosion rates reached 21.6 mm/a and 19.9 mm/a respectively at80 ℃. For 321 stainless steel, the pitting corrosion was obvious. After hot-dipped aluminum treatment, the surface of three samples had no corrosion found in the same medium for one month, and the hot-dipped aluminum coatings after simulated conditions in high temperature and high pressure autoclave did not have corrosion, either. The quality of hot-dipped aluminum coating of 20# steel, 15 CrMo steel and 321 stainless steel hydrofining heat exchangers tubes by improved technology meets the national standards. These results of corrosion test under wet ammonium chloride and simulated service condition test of high temperature and high pressure autoclave confirm that the hot-dipped aluminum coating has good anti-corrosion performance in the service environment of ammonium chloride.
The work aims to study the corrosion resistance of hydrofining heat exchangers tubes after improved hot-dipping aluminum treatment in different ammonium chloride environments, and analyze the corrosion resistance mechanism. 20# steel,15 Cr Mo steel and 321 stainless steel were treated by improved hot-dipping aluminum technology. The thickness, structure and composition of coatings were analyzed by optical microscopy, X-ray diffraction(XRD), scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS). The corrosion resistance in ammonium chloride of hot-dipped aluminum coating was evaluated by corrosion test under wet ammonium chloride and simulated service condition test of high temperature and high pressure autoclave. The obtained hot-dipped aluminum coatings on 20 # steel, 15 CrMo steel and 321 stainless steel had no surface defects, and the thickness were all over 0.080 mm. The coating structure was mainly composed of pure Al layer, Fe-Al alloy layer and a small amount of Al_2O_3. Under the condition of wet ammonium chloride, the corrosion rates of 20# steel and 15 CrMo steel increased obviously with the increasing temperature. The corrosion rates reached 21.6 mm/a and 19.9 mm/a respectively at80 ℃. For 321 stainless steel, the pitting corrosion was obvious. After hot-dipped aluminum treatment, the surface of three samples had no corrosion found in the same medium for one month, and the hot-dipped aluminum coatings after simulated conditions in high temperature and high pressure autoclave did not have corrosion, either. The quality of hot-dipped aluminum coating of 20# steel, 15 CrMo steel and 321 stainless steel hydrofining heat exchangers tubes by improved technology meets the national standards. These results of corrosion test under wet ammonium chloride and simulated service condition test of high temperature and high pressure autoclave confirm that the hot-dipped aluminum coating has good anti-corrosion performance in the service environment of ammonium chloride.
引文
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[15]夏谦,伍林伟,陈俊帆.渗铝钢与镀锌钢应用于输电线路铁塔的比较研究[J].电工技术,2018(3):115-117.XIA Qian,WU Lin-wei,CHEN Jun-fan.The comparative research on aluminized and galvanized steel in tower of transmission line[J].Electric engineering,2018(3):115-117.
[16]SUN X F,HUANG Y L,SONG W,et al.Study on thermal-shock-resistance of the composite coating of 20 steel substrate by hot dip aluminum and micro-arc oxidation[J].Key engineering materials,2016,723:450-453.
[2]王磊.炼厂静设备的腐蚀与防护[D].大连:大连理工大学,2015.WANG Lei.Corrosion and protection of static equipment in refinery[D].Dalian:Dalian University of Technology,2015.
[3]崔正丹.炼油厂水相换热器碳钢材料的腐蚀与防护措施研究[D].长沙:湖南大学,2009.CUI Zheng-dan.Corrosion and anti-corrosion of carbon steel of the aqueous phase heat-exchanger in refineries[D].Changsha:Hunan University,2009.
[4]李奇峰.常减压装置塔顶换热器管束腐蚀及选材[J].石油化工腐蚀与防护,2009,26(3):41-42.LI Qi-feng.Corrosion of atmospheric-vacuum distillation unit's overhead heat exchanger tube bundles and material selection[J].Corrosion&protection in petrochemical industry,2009,26(3):41-42.
[5]曾勇.8Mt/a常减压蒸馏装置冷换设备选材分析[J].石油化工腐蚀与防护,2006,23(4):57-60.ZENG Yong.Material selection for the heat exchange equipment of 160 000 BPSD atmospheric-vacuum distillation unit[J].Corrosion&protection in petrochemical industry,2006,23(4):57-60.
[6]于海成,严与辉,梁向荣,等.新型Ni-Cr耐蚀合金换热器管板焊接工艺评定及组织研究[J].焊接技术,2018,47(7):43-47.YU Hai-cheng,YAN Yu-hui,LIANG Xiang-rong,et al.Study on welding process assessment and microstructure of new Ni-Cr corrosion resistant alloy heat exchanger tube-sheet[J].Welding technology,2018,47(7):43-47.
[7]JIN B J,LEE J P,PARK M H,et al.A study on forming for plate-type heat exchangers of the Ti material[J].Procedia engineering,2017,174:171-178.
[8]李辉,刘希武,蒋兴家,等.表面涂层技术在石油炼制领域的应用[J].焊接技术,2018,47(10):1-5.LI Hui,LIU Xi-wu,JIANG Xing-jia,et al.Application of surface coating technology in petroleum refining[J].Welding technology,2018,47(10):1-5.
[9]王帅.防腐镀(涂)层管束表面对流凝结换热特性实验研究[D].南京:东南大学,2016.WANG Shuai.Experimental study on convectioncondensation heat transfer characteristics of different antiseptic tube surfaces[D].Nanjing:Southeast University,2016.
[10]XU X Q,MIAO J,BAI Z Q,et al.The corrosion behavior of electroless Ni-P coating in Cl-/H2S environment[J].Applied surface science,2012(22):8802-8806.
[11]朱新亮.镍磷化学镀技术在换热器管束防腐中的应用分析[J].中国石油和化工标准与质量,2013(11):32.ZHU Xin-liang.Application of electroless nickel-phosphorus plating technology in anticorrosion of heat exchanger tube[J].China petroleum and chemical standard and quality,2013(11):32.
[12]师红旗,丁毅,马立群.化学镀镍换热器管束腐蚀破裂失效分析[J].表面技术,2009,38(5):93-95.SHI Hong-qi,DING Yi,MA Li-qun.Failure analysis of corrosion cracking of heat exchanger tubes packing with electroless nickel[J].Surface technology,2009,38(5):93-95.
[13]黄卫东,张良玉,曲谦,等.热浸铝材料表面电化学氧化工艺研究[J].有色矿冶,2018,34(1):37-41.HUANG Wei-dong,ZHANG Liang-yu,QU Qian,et al.Study on electrochemical oxidation process of hot dip aluminum material[J].Non-ferrous mining and metallurgy,2018,34(1):37-41.
[14]张桂凯,李炬,陈长安.不锈钢异型件表面阻氚层制备技术的研究进展[J].机械工程材料,2010,34(4):5-10.ZHANG Gui-kai,LI Ju,CHEN Chang-an.Research progress on preparation technology of tritium penetration barrier on special-shaped pieces of stainless steel[J].Materials for mechanical engineering,2010,34(4):5-10.
[15]夏谦,伍林伟,陈俊帆.渗铝钢与镀锌钢应用于输电线路铁塔的比较研究[J].电工技术,2018(3):115-117.XIA Qian,WU Lin-wei,CHEN Jun-fan.The comparative research on aluminized and galvanized steel in tower of transmission line[J].Electric engineering,2018(3):115-117.
[16]SUN X F,HUANG Y L,SONG W,et al.Study on thermal-shock-resistance of the composite coating of 20 steel substrate by hot dip aluminum and micro-arc oxidation[J].Key engineering materials,2016,723:450-453.