304不锈钢在稀硫酸溶液中的腐蚀行为探讨

采用动电位极化曲线、电化学阻抗谱和全浸试验研究了304不锈钢在硫酸溶液中的腐蚀行为。试验结果表明:在浓度5%的硫酸溶液中,304不锈钢出现3个自腐蚀电位,分别为-0.38V、-0.14V和0.0V,为不稳定体系;电化学阻抗谱中钝化膜电阻为228.7Ω·cm2,表明不锈钢耐蚀性主要由表面钝化膜提供;浸泡试验发现在低于50%的硫酸浓度下,不锈钢的腐蚀速率随着硫酸浓度的增加而增大。     

304L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.      

5083铝镁合金在不同浓度NaCl溶液中的腐蚀研究

采用扫描电化学显微镜（SECM）中的极化曲线法和交流阻抗图谱法研究5083铝镁合金在不同浓度NaCl溶液中的腐蚀行为,结果表明:合金在中性NaCl溶液中的腐蚀为钝化材料体系,随着盐度的增加,Cl-对合金基体的破坏加剧,腐蚀电位正移,点蚀电位减小,其电化学阻抗谱中仅有1个容抗弧且呈现收缩趋势.同时,阻抗减小,相位角增加,弥散指数降低,合金的耐腐蚀性能下降.溶液中存在强活化作用的Cl-,会损坏合金表面的氧化膜,逐渐取代腐蚀产物Al（OH）₃中的OH-,生成新的腐蚀产物AlCl₃.      

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R_t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.      

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(10~1000 μg·L-1)和溶解氧质量浓度(0~200 μg·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.      

CP-Ti在含氟离子硝酸中电化学腐蚀行为

采用开路电位(OCP)、动电位极化曲线(PPC)、电化学阻抗谱(EIS) 3种电化学测试手段对工业纯钛(CP-Ti)在含氟离子硝酸溶液中的电化学腐蚀行为进行研究。结果表明:随着硝酸溶液中氟离子浓度的增加,CP-Ti耐蚀性变差;影响CP-Ti耐蚀性转变的临界氟离子浓度为1. 25 mmol/L;氟离子与CP-Ti表面的氧化膜发生反应,致使均匀、致密的氧化膜溶解转变为多孔膜,降低了CP-Ti的耐蚀性。     

辉铜矿生物浸出电化学机制及动力学研究

采用Tafel法、交流阻抗法和恒电位阶极化法研究了辉铜矿生物浸出过程电化学行为,测定了腐蚀电化学动力学参数,确定了所发生的电化学反应。并结合第一性原理计算,分析了辉铜矿晶体结构性质变化,从电子结构和电化学角度揭示了细菌、 pH值和温度等因素对辉铜矿浸出的影响规律,查明了辉铜矿浸出过程主要影响因素及控制步骤。结果表明, pH值和温度对腐蚀电流和腐蚀电位影响显著,降低pH值和升高温度,降低了化学反应的吉布斯自由能,升高了阳极腐蚀电流密度,有利于辉铜矿电化学腐蚀反应的进行。辉铜矿溶解过程中生成了大量的Cu_nS多硫产物和S膜钝化层,导致电荷传递量较少,是阻碍辉铜矿氧化溶解的关键因素。细菌的存在,氧化Fe~(2+)增加了空穴浓度,提高了反应速率。同时,提高了溶液中的电位,阻抗弧变小,促进了多硫化物和S膜的氧化,从而加速了辉铜矿的氧化溶解。     

静水压与溶解氧耦合作用对低合金高强钢腐蚀电化学行为的影响

采用动电位极化测试和扫描电子显微镜/能谱仪表征, 通过理想动电位极化曲线分析方法和微观腐蚀形貌观察研究了静水压与溶解氧耦合作用对低合金高强钢在质量分数为3.5% NaCl溶液中腐蚀电化学行为的影响. 结果表明: 随着静水压和溶解氧溶度的同时增大, 腐蚀电位先增高而后逐渐降低, 腐蚀电流呈非线性增长; 静水压与溶解氧在腐蚀过程中存在相互竞争抑制关系, 在静水压与溶解氧同时增长过程中, 溶解氧首先促进阴极反应过程并抑制阳极反应过程, 而后静水压逐渐加速阳极过程并对阴极反应过程有一定的抑制作用; 静水压与溶解氧耦合作用加速了腐蚀产物膜的生长, 增加了低合金高强钢表面点蚀坑的数量和生长尺寸.      

外加拉应力对13Cr马氏体不锈钢的腐蚀行为影响

采用电化学测试手段(开路电位、交流阻抗谱及动电位极化曲线测试), 结合接触角测试及体视显微镜微观形貌观察探究在80 g·L-1 NaCl溶液中拉应力对L80-13Cr马氏体不锈钢钝化膜溶解与再修复机制的影响.结果表明, 拉应力大小与L80-13Cr的钝化特性存在正相关关系.随着外加拉应力的增大, L80-13Cr马氏体不锈钢的开路电位负移, 电子转移电阻减小, 线性极化电阻减小, 反应速率随着拉应力的增大而增大.而L80-13Cr马氏体不锈钢在高电位下再钝化形成的钝化区会缩短, 自腐蚀电位降低, 维钝电流密度增加.接触角测试和体视显微镜微观形貌观察发现, 拉应力使得表面接触角减小, 不锈钢表面容易发生点蚀.外加拉应力使得L80-13Cr马氏体不锈钢的表面能增加, 促进钝化膜的溶解, 并且抑制钝化膜的再生, 导致材料耐蚀性降低.      

醇盐体系增材制造钛合金的电化学抛光机理

电化学抛光是增材制造TC4钛合金表面处理的方法之一.采用循环伏安、交流阻抗、计时电流及X射线光电子能谱仪(XPS)等测试方法,研究了乙二醇-氯化钠电解液中增材制造TC4钛合金的电化学抛光行为.结果表明,钛合金在乙二醇-氯化钠体系中的氧化过程是Ti→TiO→Ti₂O₃→TiO₂.施加不同的电位,影响钛合金表面氧化膜(也可称为钝化膜)厚度的演化,随着施加电位的增大,氧化膜厚度先增大后减小.根据氧化膜厚度的变化规律提出两步抛光法,与单一钝化区电位抛光相比,两步抛光法抛光速率更大.在25 min时钛合金表面取得了最佳抛光效果,此时粗糙度为2.6μm.     

Passivation Behaviors of Super Martensitic Stainless Steel in Weak Acidic and Weak Alkaline NaCl Solutions

The passivation behaviors of super martensitic stainless steels(SMSS)were studied by polarization curves at passive potential of-0.1Vand in various NaCl solutions,electrochemical impedance spectroscopy(EIS)and Xray photoelectron spectroscopy(XPS)analysis.Electrochemical test results showed that,in alkaline solutions,passivation region width was wider,passivation current was smaller,and polarization resistance was greater;thus,the passive film of SMSS in alkaline solutions had better passivation behaviors than that in acidic solutions.The polarization curve and EIS of samples SMSS1 and SMSS2were also used to study which sample had better passivation behaviors.All results demonstrated that passive film structure of SMSS1 sample was more stable,and capacity of passive film was enhanced.The impact of alloying elements on the passive film(SMSS)passivation capability was also discussed by XPS depth profiling,and XPS depth profiling showed that the composition of the passive film was mainly composed of Fe-oxide and Cr-oxide.So the passive film structures were mixed layers of Fe-oxide and Cr-oxide.Fe oxidation product and Cr oxidation product would help to improve the protective property of passive film,which could promote the formation of a passive film structure more stably and densely.     

甲酸浓度对316L不锈钢腐蚀钝化?活化转变行为的影响

为深入认识316L不锈钢在甲酸溶液中的钝化-活化转变行为,在90 ℃、质量分数为0~30%的甲酸溶液中对316L不锈钢进行全浸试验和阳极极化曲线测试。研究了甲酸质量分数对316L不锈钢腐蚀速率、腐蚀形貌、开路电位、初始钝化电位、临界电流密度、钝化电流密度和钝化膜破裂电位的影响规律,分析了H+ 和HCOO? 含量对活化区、过渡区和钝化区阳极反应的影响机制。结果表明,316L不锈钢在甲酸溶液中发生非均匀的全面腐蚀。当甲酸质量分数达到30%、腐蚀速率为1.2×10?3 mm·a?1时,316L不锈钢就具有明显的钝化?活化转变。随着甲酸质量分数增加,316L不锈钢的初始钝化电位正移、临界电流密度增大、钝化电流密度增大、钝化膜破裂电位负移。甲酸溶液中H+ 和HCOO? 含量的增加,会加速316L不锈钢活性溶解,抑制钝化膜生长,促进钝化-活化转变。      

Effect of Chloride on Semiconducting Properties of Passive Films Formed on Supermartensitic Stainless Steel in NaHCO3 Solution

 The effects of chloride ion on the electrochemical behavior and the semiconducting properties of the passive film on supermartensitic stainless steel in 0. 5 mol/L NaHCO3 solution were investigated using potentiodynamic polarization, the potentiostatic current transients and Mott-Schottky analysis. The results indicated that chloride ion narrowed passivation region and improved pitting susceptibility. The steady state current densities were independent of film-formed potentials, which was in good agreement with the assumption of the point defect model (PDM). The capacitance results showed the fact that the passive films had a multilayer character. The defect density decreased with increasing passive film formation potential. The chloride ion induced changes of the acceptor densities and donor densities of the passive films.     

Electronic Properties of Passive Films Formed on G3 and G30 Nickel-based Alloys in Bicarbonate/Carbonate Buffer Solution

The electronic properties of passive films formed on G3 and G30 alloys in bicarbonate/carbonate buffer solution were comparatively studied by electrochemical impedance spectra(EIS) and Mott-Schottky analysis, the chemical composition of the passive film formed on G3 alloy was detected by X-ray photoelectron spectroscopy (XPS). The results show that passive film on G3 alloy had better protection than that on G30 alloy. The transfer resistance, film resistance and diffusion resistance of the passive films on both alloys increased with increasing formation potential, prolonging formation time, increasing pH value, decreasing formation temperature, and decreasing chloride and sulphide ions concentration. Mott-Schottky plot reveals that the passive films on the two alloys show a p-n semi-conductive character. XPS analysis indicates that the passive film on G3 alloy was composed of an inner Cr oxide and an outer Fe, Mo/Ni oxides.     

Evaluation of corrosion response of sintered ferritic stainless steels using potentiodynamic polarization and electrochemical impedance spectroscopy techniques

The present study investigates the effect of sintering temperature on the electrochemical response of ferritic (434L) stainless steels determined through potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) studies. To understand the corrosion mechanism, the EIS was done at open circuit potential (OCP), passive region (500mV) and near breakdown potential region of polarization curve of 434L stainless steel. The compacts sintered at higher temperature (1400°C) exhibit better corrosion resistance. To explain the EIS results, an electrical circuit has been conceptualized at open circuit potential (OCP) that indicates the presence of two time constants. This can be attributed to the presence of Electrical Double Layer (EDL) and formation of a protective passive during corrosion. EIS results on compacts done at 500mV shows only one time constant which suggests nearly complete passivation of the surface due to the formation of passive film.