温度对液滴干湿循环下430不锈钢点蚀的影响
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摘要
目的研究温度对液滴干湿循环条件下点蚀临界相对湿度和再钝化临界相对湿度的影响规律,结合形貌观察分析液滴条件下点蚀的形成机理。方法首先通过多液滴电位监测的方法研究了温度对430不锈钢干湿循环中点蚀的影响。其次,利用统计学方法分析了430不锈钢干湿循环过程中发生点蚀的特征参量,如点蚀、再钝化临界相对湿度,及其对应的临界氯离子浓度。然后,通过激光共聚焦显微镜统计分析了点蚀坑的深度和直径等特征参数。最后,对比了不同温度下430不锈钢在MgCl2溶液中的动电位极化曲线。结果随着温度从10℃上升到50℃,试样发生点蚀的概率从5/35上升到25/35;点蚀平均临界相对湿度从55%上升到63%,对应氯离子浓度从7.4 mol/L下降到6.4 mol/L;再钝化平均临界相对湿度从74%上升到91%,对应氯离子浓度从5 mol/L下降至2.5 mol/L。结论温度升高加速430不锈钢点蚀生长,抑制再钝化。形貌分析表明,随温度增加,点蚀坑形态从横向生长向蚀坑深度方向加速生长。
The work aims to study the influence of temperature on the critical relative humidity of pitting corrosion and repassivation under dry and wet cycle of droplets, and to analyze the formation mechanism of pitting by observing morphology.The effect of temperature on pitting corrosion of 430 stainless steel in dry and wet cycles was studied by multi-droplet potential monitoring. Secondly, statistical method was used to analyze the characteristic parameters of pitting corrosion of 430 stainless steel during the dry and wet cycle, such as critical relative humidity of pitting corrosion, repassivation and corresponding critical chloride ion concentration. Then, the characteristic parameters such as the depth and diameter of the pitting pit were statistically analyzed by laser confocal microscopy. Finally, the potentiodynamic polarization curves of 430 stainless steel in MgCl2 solution at different temperatures were compared. As the temperature rose from 10 ℃ to 50 ℃, the probability of pitting corrosion increased from 5/35 to 25/35, the average critical relative humidity of pitting corrosion rose from 55% to 63% and the corresponding chloride ion concentration decreased from 7.4 mol/L to 6.4 mol/L; while the average critical relative humidity of repassivation increased from 74% to 91% and the corresponding chloride ion concentration decreased from 5 mol/L to 2.5 mol/L.Temperature rise accelerates the pitting growth of 430 stainless steel, but inhibits repassivation. Morphological analysis shows that with the increase of temperature, the morphology of pitting pits accelerates from lateral growth to pit depth.
The work aims to study the influence of temperature on the critical relative humidity of pitting corrosion and repassivation under dry and wet cycle of droplets, and to analyze the formation mechanism of pitting by observing morphology.The effect of temperature on pitting corrosion of 430 stainless steel in dry and wet cycles was studied by multi-droplet potential monitoring. Secondly, statistical method was used to analyze the characteristic parameters of pitting corrosion of 430 stainless steel during the dry and wet cycle, such as critical relative humidity of pitting corrosion, repassivation and corresponding critical chloride ion concentration. Then, the characteristic parameters such as the depth and diameter of the pitting pit were statistically analyzed by laser confocal microscopy. Finally, the potentiodynamic polarization curves of 430 stainless steel in MgCl2 solution at different temperatures were compared. As the temperature rose from 10 ℃ to 50 ℃, the probability of pitting corrosion increased from 5/35 to 25/35, the average critical relative humidity of pitting corrosion rose from 55% to 63% and the corresponding chloride ion concentration decreased from 7.4 mol/L to 6.4 mol/L; while the average critical relative humidity of repassivation increased from 74% to 91% and the corresponding chloride ion concentration decreased from 5 mol/L to 2.5 mol/L.Temperature rise accelerates the pitting growth of 430 stainless steel, but inhibits repassivation. Morphological analysis shows that with the increase of temperature, the morphology of pitting pits accelerates from lateral growth to pit depth.
引文
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[21]CRUZ R P V,NISHIKATA A,TSURU T.Pitting corrosion mechanism of stainless steels under wet-dry exposure in chloride-containing environments[J].Corrosion science,1998,40(1):125-139.
[2]TSUTSUMI Y,NISHIKATA A,TSURU T.Pitting corrosion mechanism of type 304 stainless steel under a droplet of chloride solutions[J].Corrosion science,2007,49(3):1394-1407.
[3]MAIER B,FRANKEL G S.Pitting corrosion of bare stainless steel 304 under chloride solution droplets[J].Journal of the Electrochemical Society,2010,157(10):302-312.
[4]HASTUTY S,TSUTSUMI Y,NISHIKATA A,et al.Pitting corrosion of type SS430 stainless steel in the process of drying of chloride solution layer[J].ISIJ International,2012,52(5):863-867.
[5]LUO H,DONG C F,LI X G,et al.The electrochemical behaviour of 2205 duplex stainless steel in alkaline solutions with different pH in the presence of chloride[J].Electrochimica acta,2012,64(1):211-220.
[6]LUO H,DONG C F,XIAO K,et al.Characterization of passive film on 2205 duplex stainless steel in sodium thiosulphate solution[J].Applied surface science,2011,258(1):631-639.
[7]MORCILLO M,CHICO B,OTERO E,et al.Effect of marine aerosol on atmospheric corrosion[J].Materials performance,1999,38(4):72.
[8]王佳,水流彻.使用Kelvin探头参比电极技术进行薄液层下电化学测量[J].中国腐蚀与防护学报,1995,15(3):173-179.WANG Jia,SHUI Liu-che.Electrochemical measurement of thin liquid layer using kelvin probe reference electrode technology[J].Journal of chinese society for corrosion and protection,1995,15(3):173-179.
[9]王燕华,张涛,王佳,等.Kelvin探头参比电极技术在大气腐蚀研究中的应用[J].中国腐蚀与防护学报,2004,24(1):59-64.WANG Yan-hua,ZHANG Tao,WANG Jia,et al.Application of kelvin probe reference electrode technology in atmospheric corrosion research[J].Journal of Chinese society for corrosion and protection,2004,24(1):59-64.
[10]STRATMANN M,STRECKEL H,KIM K T,et al.On the atmospheric corrosion of metals which are covered with thin electrolyte layers-I,verification of the experimental technique[J].Corrosion science,1990,30(6-7):681-696.
[11]STRATMANN M,STRECKEL H,KIM K T,et al.On the atmospheric corrosion of metals which are covered with thin electrolyte layers-II,experimental results[J].Corrosion science,1990,30(6-7):697-714.
[12]STRATMANN M,STRECKEL H,KIM K T,et al.On the atmospheric corrosion of metals which are covered with thin electrolyte layers-III.The measurement of polarisation curves on metal surfaces which are covered by thin electrolyte layers[J].Corrosion science,1990,30(6-7):715-734.
[13]NISHIKATA A,ICHIHARA Y,TSURU T.An application of electrochemical impedance spectroscopy to atmospheric corrosion study[J].Corrosion science,1995,37(6):897-911.
[14]SHI Y,TADA E,NISHIKATA A.Erratum:A method for determining the corrosion rate of a metal under a thin electrolyte film[J].Journal of the Electrochemical Society,2017,164(6):X10.
[15]NISHIKATA A,SUZUKI F,TSURU T.Corrosion monitoring of nickel-containing steels in marine atmospheric environment[J].Corrosion science,2005,47(10):2578-2588.
[16]STERN M.Closure to"discussion of'electrochemical polarization,1.A theoretical analysis of the shape of polarization curves'[M.Stern and A L Geary(pp.56-63,Vol.104)]"[J].Journal of the Electrochemical Society,1957,104(12):751.
[17]KEDDAM M.Whitney award lecture:application of advanced electrochemical techniques and concepts to corrosion phenomena[J].Corrosion,2006,62(12):1056-1066.
[18]NAM T V,TADA E,NISHIKATA A.Pit initiation and repassivation of stainless steels exposed to cyclic relative humidity changes[J].Journal of the Electrochemical Society,2015,162(9):419-425.
[19]CHEG C Q,KLINKENBERG L I,ISE Y,et al.Pitting corrosion of sensitised type 304 stainless steel under wet-dry cycling condition[J].Corrosion science,2017,118:217.
[20]LI S X,HIHARA L H.Atmospheric corrosion initiation on steel from predeposited NaCl salt particles in high humidity atmospheres[J].British corrosion journal,2013,45(1):49-56.
[21]CRUZ R P V,NISHIKATA A,TSURU T.Pitting corrosion mechanism of stainless steels under wet-dry exposure in chloride-containing environments[J].Corrosion science,1998,40(1):125-139.