304和316L不锈钢的高温电化学腐蚀行为

通过模拟压水堆一回路水环境,研究了溶液温度和溶氧量(DO)对304和316L不锈钢高温电化学腐蚀行为的影响.结果表明:随着溶液温度升高,在304和316L不锈钢表面所形成的氧化膜的保护性能降低;随着DO升高,304和316L不锈钢的自腐蚀电位升高,自腐蚀电流密度降低,钝化区缩小;304和316L不锈钢表面形成了双层氧化膜,外层氧化膜颗粒尺寸和颗粒间隙随着温度的升高而增大,随着DO增加而减小;在所用实验条件下,316L不锈钢表现出比304更优异的抗腐蚀性能.     

温度、氯离子和铬元素对J55油套管钢钝化膜半导体性能的影响

利用电容测量法及电化学阻抗谱技术研究了温度、氯离子浓度和铬元素对目前广泛使用的J55油套管钢在模拟土壤环境中所成钝化膜半导体性能的影响.结果表明:钝化膜呈现n型半导体特性,随着成膜温度的升高、铬元素的加入和氯离子浓度的增加,Mott-Schottky曲线直线部分的斜率减小,表明膜内杂质密度增加.阻抗谱结果表明:在同一温度下,离子在膜内的传递电阻R1随着氯离子浓度增加而减小,膜内的扩散系数YW增加;同一氯离子浓度下,随着成膜温度的升高,扩散系数YW减小.表明温度升高、溶液中氯离子浓度的增加以及铬元素的加入会使钝化膜对J55油套管钢基体的保护作用减弱.     

2507双相不锈钢在SO2污染模拟海水中的腐蚀行为

采用开路电位、电化学阻抗谱(EIS)、Mott-Schottky曲线和浸泡腐蚀实验研究了2507双相不锈钢在含不同浓度(0,0.001和0.01 mol·L-1)NaHSO3模拟海水中的腐蚀行为.研究表明:开路电位随NaHSO3浓度的增加而负移,腐蚀倾向增大;电荷转移电阻Rt随浓度的增加而减小,耐蚀性降低;2507不锈钢的腐蚀形态为局部腐蚀,点蚀程度随浓度升高有所加剧,腐蚀速率随浓度的增加而增大;Mott-Schottky曲线和成膜后电化学阻抗谱测试表明,NaHSO3的加入增加了2507不锈钢表面钝化膜的点缺陷浓度,降低了钝化膜的稳定性,电荷转移阻力减小,腐蚀更容易发生.这可能归因于NaHSO3的加入增加了模拟海水的酸度,并随NaHSO3浓度的增加促进了不锈钢表面钝化膜的破坏.     

304 L不锈钢焊缝在混凝土模拟孔隙液中的点蚀行为

采用动电位极化曲线、电化学阻抗谱、Mott-Schottky曲线等电化学方法研究了以308 L为焊丝的304 L不锈钢焊接接头在不同氯离子含量的混凝土模拟孔隙液中腐蚀行为和电化学规律。随Cl-增加,304 L不锈钢焊接接头的三个区域(母材、焊缝和热影响区)在混凝土模拟孔隙液中的自腐蚀电位、点蚀电位及电荷转移电阻降低,钝化膜中载流子密度和焊接接头的点蚀坑数量增加。在同浓度的腐蚀溶液中,308 L的焊缝区域耐蚀性最佳,热影响区次之,304 L基体表现出低的电荷转移电阻和高的掺杂浓度使得母材的耐蚀性最差。     

静水压力对304不锈钢腐蚀行为的影响

利用自制的腐蚀实验高压釜模拟深海低温高压化学环境,研究静水压力对304不锈钢腐蚀行为影响机制.利用电化学工作站对腐蚀过程进行原位检测和加速实验,得到交流阻抗谱和动电位极化曲线,通过等效电路拟合和Tafel外推法对数据进行处理.分析了腐蚀发生的热力学倾向和动力学过程,讨论了钝化膜状态对腐蚀的影响.常压环境下,自腐蚀电位高,容抗弧半径较小.氧气等气体分子容易在304不锈钢表面吸附,增大腐蚀发生的热力学倾向.随着静水压力的增加,自腐蚀电位变化不大,压力变化不会导致钝化膜性质的改变.但腐蚀电流密度从3.838×10-8 A/cm2增加到1.197×10-7 A/cm2,容抗弧半径减小,金属/钝化膜/溶液之间电位差降低,钝化膜溶解速率大于生长速率,导致钝化膜厚度减小,使304不锈钢腐蚀加剧.     

X80管线钢钝化膜电化学性能的EIS研究

目的 研究成膜电位、温度和氯离子等对X80管线钢在1 mol/L NaHCO3/0.5 mol/L Na2CO3缓冲溶液中所形成的钝化膜的电化学性能的影响.方法 利用电化学阻抗谱技术研究了X80管线钢在1 mol/L NaHCO3/0.5 mol/L Na2CO3缓冲溶液中所形成的钝化膜的电化学性能.结果 随着成膜电位的增加,传递电阻R1减小,而膜电阻R2和扩散阻抗YW增加,表明膜的致密性增加;成膜温度升高,传递电阻R1、膜电容Q2和膜电阻.尺2减小,说明膜的致密性减小;同一温度下增加溶液中的氯离子浓度,传递电阻R1、膜电容Q2和膜电阻R2:均减小;在同一氯离子浓度下升高温度,传递电阻R1、膜电容Q2:和膜电阻R2:均减小.结论 成膜电位、成膜温度和氯离子会对钝化膜的电化学性能产生显著的影响.     

氯离子对石油测井仪器用Cr13不锈钢点损伤行为的影响

采用高温高压模拟环境装置和实时动电位极化和交流阻抗技术对石油测井仪器用Cr13不锈钢在模拟井下不同氯离子环境中电极的腐蚀失重和电化学行为进行了研究.实验结果表明,当地层水或者钻井液中氯离子浓度较高时,Cr13不锈钢表面的点损伤难以避免;随着氯离子浓度的升高,Cr13的均匀腐蚀速率增大,试样表面点蚀坑增多;局部氯离子以FeCl2和FeCl3形式吸附是造成钝化膜损伤的主要原因.应尽量减少仪器在含氯离子环境中的停留时间或提高材料等级.     

压水堆一回路主管道316 L不锈钢的电化学腐蚀行为

通过中心复合设计试验法设计试验,结合动电位极化曲线和电化学阻抗谱的测量以及氧化膜形貌观察和成分测量,研究了温度(30~350℃)、Cl-质量浓度(10~1000μg·L-1)和溶解氧质量浓度(0~200μg·L-1)3种因素对压水堆一回路主管道316L不锈钢电化学腐蚀性能的影响.结果表明:温度是影响316L不锈钢电化学腐蚀性能最显著的因素,温度越高,腐蚀电流密度越大,点蚀电位越低;Cl-浓度和溶解氧浓度对316L不锈钢电化学腐蚀性能的影响与温度密切相关,温度较低时(T<150℃),Cl-浓度和溶解氧浓度均对316L腐蚀电流密度几乎无影响,但点蚀电位却随Cl-浓度增加和溶解氧浓度的降低而降低;温度较高时,分别为T>130℃和T>150℃,Cl-浓度和溶解氧浓度均对316L点蚀电位几乎无影响,但腐蚀电流密度却随Cl-和溶解氧的浓度增加而显著增加,腐蚀加剧.电化学阻抗谱的测量和氧化膜形貌的观察也进一步验证了上述试验结果.     

有菌和无菌体系下磁黄铁矿氧化的电化学研究

在有菌和无菌酸性体系下,对磁黄铁矿电化学氧化进行研究。研究结果表明:在磁黄铁矿被氧化过程中伴随元素S的生成,覆盖于电极表面,使电极表面发生钝化;随着电位的升高,元素S被氧化成SO42-,钝化膜被击穿;氧化亚铁硫杆菌作用后增强了磁黄铁矿的反应性能,促进了磁黄铁矿氧化反应速度,腐蚀反应速度明显提高,但细菌对磁黄铁矿电极的氧化还原反应过程机理并没有产生影响;在相同电位下,有细菌时的阻抗明显低于无细菌时的阻抗,细菌的存在加速了表面物质的扩散,电极过程受电化学步骤控制,测定结果与线性扫描所得结果一致。     

模拟孔溶液中球墨铸铁表面钝化膜脱钝过程及氯离子阈值分析

为了揭示输水过程中内衬水泥砂浆球墨铸铁管的腐蚀机理,开展了球墨铸铁样品在模拟砂浆孔溶液中的腐蚀实验.采用电化学测试方法,研究了模拟孔溶液中球墨铸铁表面钝化膜的脱钝过程,分析了模拟孔溶液碱度和氯离子浓度对球墨铸铁电化学阻抗谱及极化电阻的影响.结果表明:当模拟孔溶液的pH值从13.6降低至11.5时,球墨铸铁表面钝化膜脱钝时的氯离子浓度从0.30 mol/L减小至0,且脱钝时的球墨铸铁阻抗谱和极化电阻发生明显改变;球墨铸铁表面脱钝氯离子阈值与溶液的pH值呈线性关系,且随pH值的降低而减小.所建立的球墨铸铁表面脱钝氯离子阈值方程,为进一步评估内衬水泥砂浆球墨铸铁管的服役寿命提供依据.     

Study on the passive film formed on 2205 stainless steel in acetic acid by AAS and XPS

The properties of the passive film formed on 2205 stainless steel in acetic acid at high temperature that contained chloride ions were studied by atomic absorption spectrometry (AAS), X-ray photoelectron spectroscopy (XPS), and electrochemical polarization measurements. AAS results show that molybdenum is enriched on the surface as the passive film is dissolved. This enrichment decreases the corrosion resistance because it hinders chloride adsorption and Fe ion dissolution, and acts as a local pH buffer because it consumes protons. The dissolution ratio of Fe/Cr is approximately 10 during the active dissolution of the passive film. XPS results indicate that when the potential is in the passivation region, Cr comprises about 50% of the metal cations in the near-surface region of the passive film and is the main metal constituent in this region. When the polarization potential is much greater than the transpassivation potential, the Mo content accounts for approximately 45% of the metal cations in the nearurface region; Fe and Ni have no obvious influence on the formation, dissolution, or puncture of the passive film.     

核电蒸汽发生器690合金管在高温高压水中的腐蚀电化学行为

通过模拟压水堆一回路水环境,研究了溶液温度(25~285°C)和溶解氧(DO)(20μg/L,2.1mg/L,8.4mg/L)对690合金电化学腐蚀行为的影响,及690合金在一回路水环境中的均匀腐蚀行为.极化曲线和光电子能谱的结果分析表明:随着溶液温度的升高,690合金的自腐蚀电位下降,自腐蚀电流密度增大,钝化区缩小;随着DO的升高,690合金的自腐蚀电位升高,自腐蚀电流密度降低,钝化区缩小;690合金在一回路水环境中的均匀腐蚀速率为0.244mg/(dm2·h1/2),形成了外层富Fe、Cr和Ni的氢氧化物和内层富Fe、Cr和Ni的金属氧化物的氧化膜.     

胶凝材料组成对钢筋混凝土耐久性的影响

利用电化学阻抗法和压汞法等研究了外渗氯盐条件下胶凝材料组成对钢筋混凝土耐久性的影响,结果表明:随胶凝材料中粉煤灰或矿渣含量的提高,钢筋混凝土耐久性、混凝土电阻率和钢筋电荷转移电阻先增加后减少,钢筋腐蚀速率则先减少后增加;氯离子临界浓度随钢筋周围溶解氧含量的提高及Ca(OH)2含量的降低而降低;掺合料取代部分水泥后提高了混凝土的致密性,增大了电荷转移电阻,提高了钝化膜的稳定性,同时会降低混凝土内的Ca(OH)2含量,引起氯离子临界浓度下降.     

用于散热器的冷轧钢板耐蚀性

利用化学浸泡及电化学方法研究了４种钢制散热器材质在不同含氧量和氯离子浓度下的腐蚀速度及耐蚀性，并用Ｘ射线衍射对锈蚀物进行了结构分析。实验结果表明，钢材腐蚀速度主要取决于供热水系统中的溶氧量。在脱氧条件下则形成Ｆｅ３Ｏ４保护膜，此时氯离子将加速材料的腐蚀。腐蚀极化电阻则随残余应力的增加而下降。     

Corrosion behavior of ferritic stainless steel with 15wt% chromium for the automobile exhaust system

The effect of chloride ion concentration, pH value, and grain size on the pitting corrosion resistance of a new ferritic stainless steel with 15wt% Cr was investigated using the anodic polarization method. The semiconducting properties of passive films with different chloride ion concentrations were performed using capacitance measurement and Mott-Schottky analysis methods. The aging precipitation and intergranular corrosion behavior were evaluated at 400–900℃. It is found that the pitting potential decreases when the grain size increases. With the increase in chloride ion concentration, the doping density and the flat-bland potential increase but the thickness of the space charge layer decreases. The pitting corrosion resistance increases rapidly with the decrease in pH value. Precipitants is identified as Nb(C,N) and NbC, rather than Cr-carbide. The intergranular corrosion is attributed to the synergistic effects of Nb(C,N) and NbC precipitates and Cr segregation adjacent to the precipitates.     

Passivity breakdown of 13Cr stainless steel under high chloride and CO_2 environment

Herein, the effect of high chloride ion(Cl~-) concentration on the corrosion behavior and passive film breakdown of 13Cr martensitic stainless steel under CO_2 environment was demonstrated. The Cl~- concentration was varied from 30 to 150 g/L and cyclic potentiodynamic polarization was conducted to investigate the influence of the Cl~- concentration on the corrosion potential(E_(corr)), passive breakdown potential(E_(pit)), and repassivation potential(E_(rep)). The results of the polarization curves revealed that 13Cr stainless steel is susceptible to pitting under high Cl~- concentration. The passive breakdown potential and repassivation potential decreased with the increase of Cl-concentration. The semiconducting behavior of the passive film was investigated by Mott-Schottky analysis and the point defect model(PDM). It was observed that the iron cation vacancies and oxygen vacancies were continuously generated by autocatalytic reactions and the higher Cl~- concentration resulted in higher vacancies in the passive film. Once the excess vacancies condensed at the metal/film interface, the passive film became locally detached from the metal, which led to the breakdown of the passive film.     

Damage mechanism at different transpassive potentials of solution-annealed 316 and 316l stainless steels

Electrochemical impedance spectroscopy (EIS), anodic polarization and scanning electron microscopy techniques were used to investigate the damage mechanism in the transpassive potential region of AISI 316 and AISI 316L solution-annealed stainless steels (SS) with different degrees of sensitization. Depending on the DC potential applied during EIS tests, the AC responses in the transpassive region included three different regions:the first one associated with anodic dissolution of the passive layer, the second one contributed to the dissolution at the area near grain boundaries, and the last one attributed to pitting corrosion. In addition, the fitting results to experimental data showed that as the DC bias during the EIS test increases the charge transfer resistance (R_ct) decreases. Moreover, the R_ct values decreased as the sensitization temperature increases but the AISI 316L SS samples exhibited a higher resistance to intergranular corrosion than 316 SS samples.