pH对Q235B钢在船舶尾气脱硫液中电化学腐蚀行为的影响
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摘要
目的研究pH值对Q235B钢在脱硫液中腐蚀行为的影响,为后续工艺参数控制与防护方案设计奠定基础。方法开展浸泡实验和电化学实验,研究Q235B钢在不同pH值脱硫液中的腐蚀行为,并通过电子扫描显微镜与能谱仪,对不同pH值下腐蚀产物的形貌与元素组成进行分析。结果失重法测定Q235B钢的腐蚀速率时,腐蚀速率随pH值的升高而减小,且变化幅度越来越小。电化学测试中,Q235B钢在脱硫液中的开路电位随pH值的升高而正移,极化曲线测试没有出现钝化区,自腐蚀电位也随pH值的升高不断正移,而腐蚀电流密度反之。Nyquist图为非标准的半圆形容抗弧,随pH值的升高而不断扩大。通过扫描电镜观察,pH为4.0时,腐蚀产物较少且零星分布在碳钢表面,结构形似花蕾且空隙较多;随着pH值的升高,腐蚀产物显著增多,结构发生改变;当pH为10.0时,碳钢表面覆盖一层红褐色的产物,结构呈球状且紧密堆积。能谱分析显示:腐蚀产物主要由Fe和O元素构成,随着pH值升高,两者含量在产物中的占比不断增加;另外,还含有少量的Na、S和Zn元素。结论在所研究的pH值范围内,Q235B钢在脱硫液中的腐蚀速率随pH值的升高而降低,腐蚀受到不同程度的抑制。pH值的升高能促进生成有效且致密的腐蚀产物层。在pH值较低时,Q235B钢的腐蚀主要受阳极活化控制;随着pH值的升高,溶液中OH-浓度增大,腐蚀主要受阴极氧去极化控制,耐腐蚀性能增强,腐蚀速率减小。
The work aims to study the effect of pH value on corrosion behavior of Q235 B steel in desulfurizing liquid, in order to lay the foundation for optimizing the subsequent process parameters and designing the protection coating.Immersion test and electrochemical measurement were conducted to study the corrosion behavior of Q235B steel in desulfurizing liquid with different pH values.The morphologies and element composition of corrosion products in different pH values were analyzed by SEM and EDS.When the corrosion rate of Q235B steel was measured by weight loss method,the corrosion rate decreased with the increase of pH value and change range became smaller.In the electrochemical test,the open circuit potential of Q235B steel in desulfurization solution positively shifted with the increase of pH value.There was no passivation area in the polarization curve.Self-corrosion potential positively shifted with the increase of pH value,whereas corrosion current density was on the contrary.The Nyquist graph was a nonstandard semicircular captance arc which increased with the increase of pH value.Through observation by scanning electron microscope,when pH was 4.0,corrosion products were scattered on the surface of steel and the structural shape looked like bud with void.With the increase of pH value,the corrosion products obviously increased and the structure also changed.When pH was 10.0,the steel surface was covered by a layer of rufous products,whose structure was spherical and compacted.The EDS analysis showed that corrosion products were mainly composed of Fe and O.With the increase of pH value,the proportion increased.What’s more,there was a small amount of Na,S and Zn elements.In the range of studied pH values,corrosion rate of Q235B steel in desulfurizing liquid decreases with the increase of pH value,and the corrosion is inhibited to different degrees.The increase of pH value can promote the formation of effective and compact corrosion products layers.When the pH value is lower,the corrosion of Q235B steel is mainly controlled by anode activation.With the increase of pH value,concentration of OH-increases,corrosion is controlled by cathodic oxygen depolarization,corrosion resistance is enhanced and corrosion rate declines.
The work aims to study the effect of pH value on corrosion behavior of Q235 B steel in desulfurizing liquid, in order to lay the foundation for optimizing the subsequent process parameters and designing the protection coating.Immersion test and electrochemical measurement were conducted to study the corrosion behavior of Q235B steel in desulfurizing liquid with different pH values.The morphologies and element composition of corrosion products in different pH values were analyzed by SEM and EDS.When the corrosion rate of Q235B steel was measured by weight loss method,the corrosion rate decreased with the increase of pH value and change range became smaller.In the electrochemical test,the open circuit potential of Q235B steel in desulfurization solution positively shifted with the increase of pH value.There was no passivation area in the polarization curve.Self-corrosion potential positively shifted with the increase of pH value,whereas corrosion current density was on the contrary.The Nyquist graph was a nonstandard semicircular captance arc which increased with the increase of pH value.Through observation by scanning electron microscope,when pH was 4.0,corrosion products were scattered on the surface of steel and the structural shape looked like bud with void.With the increase of pH value,the corrosion products obviously increased and the structure also changed.When pH was 10.0,the steel surface was covered by a layer of rufous products,whose structure was spherical and compacted.The EDS analysis showed that corrosion products were mainly composed of Fe and O.With the increase of pH value,the proportion increased.What’s more,there was a small amount of Na,S and Zn elements.In the range of studied pH values,corrosion rate of Q235B steel in desulfurizing liquid decreases with the increase of pH value,and the corrosion is inhibited to different degrees.The increase of pH value can promote the formation of effective and compact corrosion products layers.When the pH value is lower,the corrosion of Q235B steel is mainly controlled by anode activation.With the increase of pH value,concentration of OH-increases,corrosion is controlled by cathodic oxygen depolarization,corrosion resistance is enhanced and corrosion rate declines.
引文
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[17]蔡婷婷,杨云,李艳芳,等.电镀电流密度对铝锰合金镀层耐蚀性的影响[J].表面技术,2017,46(12):245-250.CAI T T,YANG Y,LI Y F,et al.Effects of electroplating current density on corrosion resistance of aluminummagnesium alloy[J].Surface technology,2017,46(12):245-250.
[2]CHIDIEBERE M A,OGUZIE E E,LIU L,et al.Adsorption and corrosion inhibiting effect of riboflavin on Q235mild steel corrosion in acidic environments[J].Materials chemistry&physics,2015,156:95-104.
[3]张文建,吴明,谢飞,等.X80管线钢在不同pH满洲里土壤模拟溶液中的腐蚀行为[J].机械工程材料,2016,40(5):81-85.ZHANG W J,WU M,XIE F,et al.Corrosion behavior of X80 pipeline steel in simulated manzhouli soil solution with different pH[J].Materials for mechanical engineering,2016,40(5):81-85.
[4]MOUSSA S O,HOCKING M G.The photo-inhibition of localized corrosion of 304 stainless steel in sodium chloride environment[J].Corrosion science,2001,43(11):2037-2047.
[5]SAITOU M,OSHIKAWA W,ISHIKAWA T.Anomalous dimension in pitting corrosion of SUS304 in a NaCl solution[J].Corrosion science,2002,44(7):1469-1475.
[6]赵景茂,左禹,熊金平,等.p H值对低碳钢在高含盐污水中的腐蚀影响[J].材料保护,2001,34(7):8-9.ZHAO J M,ZUO Y,XIONG J P,et al.Effect of pH value on corrosion of low carbon steel in high salt waste water[J].Material protection,2001,34(7):8-9.
[7]张皓玥,王津梅.金属缝隙腐蚀的成因及实验验证[J].表面技术,2017,46(2):204-207.ZHAO H Y,WANG J M.Cause of metal crevice corrosion and experiment verification[J].Surface technology,2017,46(2):204-207.
[8]ALFA L.Understanding exhaust gas treatment systems guidance for ship owners and operators[M].London:Lloyds Register of Shipping,2012.
[9]宋春晖,黄峰,刘静,等.pH值对X120钢在模拟鹰潭酸性土壤溶液中电化学行为的影响[J].腐蚀与防护,2011,32(5):335-339.SONG C H,HUANG F,LIU J,et al.Influence of pH on electrochemical behavior of X120 steel in simulated Yingtan[J].Corrosion and protection,2011,32(5):335-339.
[10]KUANG W,MATHEWS J A,MACDONALD D D.The effect of anodamine on the corrosion behavior of 1018mild steel in deionized water:Immersion and polarization tests[J].Electrochimica acta,2014,127(5):79-85.
[11]LIU Z Y,LI X G,DU C W,et al.Local additional potential model for effect of strain rate on SCC of pipeline steel in an acidic soil solution[J].Corrosion science,2009,51(12):2863-2871.
[12]林玉珍,杨德钧.腐蚀和腐蚀控制原理[M].北京:中国石化出版社,2007:203-209.LIN Y Z,YANG D J.Corrosion and the principle of corrosion control[M].Beijing:Sinopec Press,2007:203-209.
[13]TANG J,SHAO Y,GUO J,et al.The effect of H2S concentration on the corrosion behavior of carbon steel at90℃[J].Corrosion science,2010,52(6):2050-2058.
[14]LIU J,LI X,LIN Y,et al.Study of cavitation corrosion behaviors and mechanism of carbon steel in neutral sodium chloride aqueous solution[J].Corrosion,2005,61(11):1061-1069.
[15]谢飞,杨晓峰,王丹,等.库尔勒土壤模拟溶液的pH对X80管线钢电化学腐蚀行为的影响[J].机械工程材料,2015,39(4):59-62.XIE F,YANG X F,WANG D,et al.Effect of pH value on electrochemical corrosion behavior of X80 pipeline steel in simulated Ku’erle soil solution[J].Materials for mechanical engineering,2015,39(4):59-62.
[16]XU C M,LI R B,WANG J L,et al.Effect of microstructures on corrosion of X80 pipeline steel in an alkaline soil[J].Advanced materials research,2012,476-478:321-328.
[17]蔡婷婷,杨云,李艳芳,等.电镀电流密度对铝锰合金镀层耐蚀性的影响[J].表面技术,2017,46(12):245-250.CAI T T,YANG Y,LI Y F,et al.Effects of electroplating current density on corrosion resistance of aluminummagnesium alloy[J].Surface technology,2017,46(12):245-250.