铜镍合金在NaCl溶液中点蚀行为的研究

对铜镍合金BFe30-1-1在NaCl溶液中出现的点腐蚀行为进行了研究.首先测试其在不同pH值的0.5 mol/L Nacl溶液中的阳极极化曲线以确定点蚀电位,并在点蚀电位之上进行恒电位腐蚀.通过原子吸收光谱测定腐蚀后溶液中的Cu2 和Ni2 含量,采用扫描电镜进行形貌观察以及分析试样断面的微区成分,并对点蚀坑内的腐蚀产物进行X射线衍射分析,以了解不同条件下铜镍合金的点腐蚀行为.结果表明,BFe30-1-1合金在酸性和弱碱性的0.5 mol/L NaCl溶液中的腐蚀规律基本相似;在强碱性溶液中的低电位下,合金表面可以形成较稳定的钝化膜,因而耐腐蚀性能较好;铜镍合金BFe30-1-1的点蚀坑内发生了脱镍腐蚀.     

三乙醇胺对镁合金的缓蚀效果及其吸附行为研究

为了研究三乙醇胺在氯化钠溶液中对镁合金的缓蚀效果,运用电化学工作站和扫描电子显微镜测试分析了镁合金在含三乙醇胺的氯化钠溶液中的微分电容曲线、表面覆盖度、循环极化曲线、电化学阻抗谱和表面微观形貌。结果表明:在氯化钠溶液中添加3 m L/L三乙醇胺时,镁合金与溶液界面的微分电容值减小,微分电容曲线出现电位平台,零电荷电位正移;随着阳极极化加强,三乙醇胺在镁合金表面覆盖度下降,产生阳极脱附现象;随着浸泡时间延长,镁合金表面出现裂缝,并逐渐发展为腐蚀孔,腐蚀产物分布在蚀孔周边,且易脱落。     

溶解氧对碳锰钢点蚀电位测定的影响

选择常用的碳素船体钢和锰系船体钢各一种,在除氧及不除氧的3%NaC l溶液中进行了极化试验,测定了钢的点蚀电位,并利用电子探针分析了腐蚀形貌。结果表明,钢样在除氧溶液中的阳极极化是典型的钝化-点蚀过程;在相同的电位区间,钢样在不除氧的溶液中的表观极化行为与前者截然不同,但是钢样自身的极化过程仍是钝化-点蚀过程,点蚀仍是由钢中的夹杂物诱发,所测点蚀电位值比溶液除氧条件下的结果更正;在有溶解氧条件下测得的点蚀电位同样可以比较不同钢之间的点蚀诱发敏感性,其结果更方便、准确。     

碳钢中夹杂物诱发点蚀的规律和特性研究

选用5种低碳钢，通过浸泡试验、显微腐蚀试验和极化试验，考察了碳钢在3％NaCl(质量分数，下同)溶液中夹杂物诱发点蚀的规律和特点．结果表明：样品刚浸入溶液时其最初电位高于点蚀电位，钢中一些夹杂物活化，先诱发点蚀；局部活化使钢样的电位迅速下降，当降至点蚀电位之下，未发生点蚀或未充分诱发点蚀的夹杂物受到保护，不再活化；在阳极极化试验中，当钢样的电位极化到点蚀电位或点蚀电位以上，钢中的夹杂物几乎都会活化而诱发点蚀．     

铝电解电容器用不同工艺腐蚀箔的对比研究

利用金相显微镜分析软质交流腐蚀箔、直交流腐蚀箔及硬质交流腐蚀箔的表面及断面蚀孔形貌,监测腐蚀箔恒电流阳极氧化过程中的升压曲线,并测试腐蚀箔阳极氧化后的比容、漏电流、抗拉强度及折弯次数.结果表明,软质交流腐蚀箔的蚀孔形貌呈灌木状;直-交流腐蚀箔的蚀孔呈乔木和灌木状分布,蚀孔中有部分大而稀疏的隧道孔,扩面倍率最小;而硬质交流腐蚀箔的蚀孔呈蜂窝状,孔洞细密,扩面倍率最大.直-交流腐蚀箔的漏电流最小,硬质交流腐蚀箔的抗拉强度及折弯次数最大.     

氯化钠浓度和温度对超高强铝合金腐蚀性能的影响

采用开路电位时间曲线和动电位极化手段表征了氯化钠浓度(0%、2%、3.5%和5%均为质量分数)、温度(15℃、25℃、35℃、45℃和60℃)对7B50铝合金电化学腐蚀性能的影响。结果表明:随着氯化钠浓度增大和温度升高,超高强铝合金腐蚀敏感性逐渐增大。氯离子浓度增大,开路电位OCP和自腐蚀电位Ecorr逐渐负移,阳极极化电流逐渐增大,表明铝合金的腐蚀速率逐渐增大;当温度低于35℃,极化曲线上观察不到点蚀电位,温度必须达到45℃才开始出现明显的点蚀电位Epit,且随着温度进一步升高,点蚀电位负移。     

酸性溶液中Cl-含量和温度对PH13-8Mo腐蚀行为的影响

为了解决在深海油气钻采中出现的酸性环境中对钻采设备的腐蚀问题,结合海洋中油气田的实际环境,在pH值为3的Na2SO4+H2SO4溶液中,采用电化学极化曲线、循环极化曲线、电化学阻抗谱(EIS)结合静态浸泡实验,分别研究了Cl-质量分数(1%、3.5%和7%)和溶液温度(4、25、50和80℃)对马氏体沉淀硬化不锈钢PH13-8Mo电化学腐蚀行为的影响,并采用点缺陷PDM模型结合闭塞电池理论对其腐蚀机理进行了分析.结果表明,随着溶液中Cl-浓度的升高,PH13-8Mo极化曲线中二次钝化的特性消失.溶液中Cl-浓度和温度的升高均使得PH13-8Mo的点蚀电位降低、点蚀保护电位降低,抗点蚀能力下降,腐蚀电流密度增大,钝化电位区间缩短,电荷转移电阻呈指数关系下降,样品表面腐蚀形貌由点蚀发展为全面腐蚀.     

马氏体相变对孔蚀闭塞区化学和电化学行为的影响

采用模拟闭塞电池法和模拟闭塞溶液法研究了奥氏体304不锈钢形变诱发马氏体相变对孔蚀闭塞区化学和电化学行为的影响。为了模拟闭塞区内外间的电偶电流，对试件通入电流进行阳极极化。结果表明，与未形变的304不锈钢的试验结果相比，随着马氏体含量的增加，闭塞区溶液pH值下降，Cl^-迁入闭塞区的量更多。马氏体相的存在增强了材料的电化学活性，使其在模拟闭塞溶液中的自腐蚀电位负移，维钝电流密度增加，加速了闭塞区金属阳极溶解，促进了孔蚀的发展。     

AM60B镁合金在不同pH值酸雨中的腐蚀行为

重庆是我国镁合金产业化的重要基地,酸雨对镁合金的腐蚀非常严重.采用极化曲线和电化学交流阻抗法研究了不同pH值条件下AM60B镁合金在模拟酸雨中的腐蚀行为,用扫描电镜(SEM)观察了镁合金的腐蚀形貌,用x射线衍射仪(XRD)分析了腐蚀产物的组成.结果表明:随着溶液pH值的下降,AM60B镁合金的自腐蚀电位变负,腐蚀速率增加,同一腐蚀电位下阳极极化电流变大;电化学阻抗谱显示其容抗减小,膜电容下降,镁合金表面的保护膜被破坏;AM60B镁合金在模拟酸雨中的腐蚀以点蚀为主,形成了较深的腐蚀坑,腐蚀程度随着溶液pH值下降而增大,腐蚀产物主要由MgO和MgAl2(SO4)4·2H2O组成.     

触变成形AZ91D镁合金在NaCl溶液中腐蚀行为的电化学分析

用动电位极化曲线和电化学阻抗谱的方法对触变成形AZ91D镁合金在NaCl水溶液中腐蚀行为进行了研究.结果表明:在相同浓度的NaCl水溶液中,随着腐蚀时间的延长,开路电位逐渐提高(正移),同一腐蚀电位下触变成形AZ91 D镁合金的阳极极化电流明显减小,电化学阻抗谱(EIS)显示其容抗减小,腐蚀产物在合金表面沉积,对基体金属具有一定的保护作用,因而其腐蚀速度减小;随着溶液中Cl-浓度的增大,开路电位呈下降(负移)趋势,且其开路电位的正移速度较慢,同一腐蚀电位下触变成形AZ91D镁合金的阳极极化电流增大,EIS显示其线性阻抗减小,腐蚀反应的过程加快,所以腐蚀速度增大.     

Growth and passivation of aluminum etch tunnels at on-off controlling DC

In order to control the length of tunnels within Al foil etched in HCl-H₂SO₄ solutions, the influence of on-off control of the DC on growth and passivation of tunnels has been investigated. From SEM of oxide replicas of tunnels, it was found that, in a given etchant solution at a special temperature, the longest tunnel length depended only on the turn-on interval of DC, and the number of pits was determined by the total electricity of the DC. The corresponding mechanism is that the potential of Al foil changed rapidly at the point of the switch of DC by the result according to the anodic polarization curve and potential-time (E-t) response curves. The moment the DC was switched on, the potential increased immediately over pitting potential, leading to nucleation of pits at the surface and growth of tunnels at special lengths. When the DC was switched off, the potential rapidly decreased to a passive state, leading to the cessation of nucleation and the death of tunnels. Therefore, the longest tunnel length can be controlled and a non-piercing layer can be obtained. Furthermore, consequent etching of Al foil by the on-off control of the DC is beneficial for maintaining a good mechanical strength.     

Growth and passivation of aluminum etch tunnels at on-off controlling DC

In order to control the length of tunnels within Al foil etched in HCl-H₂SO₄ solutions, the influence of on-off control of the DC on growth and passivation of tunnels has been investigated. From SEM of oxide replicas of tunnels, it was found that, in a given etchant solution at a special temperature, the longest tunnel length depended only on the turn-on interval of DC, and the number of pits was determined by the total electricity of the DC. The corresponding mechanism is that the potential of Al foil changed rapidly at the point of the switch of DC by the result according to the anodic polarization curve and potential-time (E-t) response curves. The moment the DC was switched on, the potential increased immediately over pitting potential, leading to nucleation of pits at the surface and growth of tunnels at special lengths. When the DC was switched off, the potential rapidly decreased to a passive state, leading to the cessation of nucleation and the death of tunnels. Therefore, the longest tunnel length can be controlled and a non-piercing layer can be obtained. Furthermore, consequent etching of Al foil by the on-off control of the DC is beneficial for maintaining a good mechanical strength.     

Pitting Corrosion of Cu-Zn-Al Shape Memory Alloy in Simulated Uterine Fluid

Electrochemical test technology and surface analysis method were employed to investigate the pitting corrosion of Cu-Zn-AI shape memory alloy in simulated uterine fluid. The results showed that the breakage of the breaking-renovating equilibrium of surface layers resulted in the pitting corrosion of Cu-Zn-AI shape memory alloy in simulated uterine fluid. The development of pitting corrosion was controlled by dissolution of surface layers. The critical pitting corrosion potential was 1.70 VSCE. The kinetics equation for the development of pitting corrosion for Cu-Zn-AI shape memory alloy in simulated uterine fluid was io=465.68 t-0.5+1.5. Pitting appearances of pits could be two types: tortoise-shell, and anomaly abscess. Cl- ion facilitated the pitting corrosion of Cu-Zn-AI shape memory alloy by competing adsorption and concentrating on alloy surface at high positive potential.     

Analysis of corrosion of hot-rolled X70 steel plate during storage

In this work, analysis was performed to investigate the reason resulting in corrosion, especially pitting corrosion, of a stock of hot-rolled X70 steel plates after 4 months of storage in a warehouse. Results demonstrated that corrosion and pitting corrosion of X70 steel plate during storage is attributed to the remnant and concentration of cooling water on the top surface of the plate. Pitting corrosion occurs locally at defects on surface deposit that is generated during corrosion of the steel. The small anode vs. big cathode geometry enhances the pitting corrosion process. Chloride ions enter the pits to maintain the charge-neutrality, while ferrous ions that are generated during corrosion diffuse out of the pits to result in corrosion product layer at pit mouth.     

Pitting Corrosion Behaviour of Monel-400 Alloy in Chloride Solutions

1-IntroductionPittingcorrosionisthemostdestructiveformamongthedifferentformsoflocalizedcorrosionofmetals.Thebreakdownofthepassivefilmbyag-gressiveionssuchaschlorideionscanleadtohighpenetrationrates.Copper-nickelalloysarewidelyusedascorrosionresistantmaterialsinmarineengineering.Theircor-rosionratesdecreasesharplywithincresingNicon-tent.AseriesofCu-Nialloyshavebeenwidely.tudi.d[1~12]innaturalseawaterandinNaClsolu-tionsusingdifferentelectrochemicalmethods.Con-tradictoryresultshavebeenobtained…     

Interactions of different types of localized corrosion in surgical implants

Surgical implants often show different types of localized corrosion such as corrosion fatigue cracking, pitting and crevice corrosion on the same part. Interactions of these different corrosion phenomena were investigated. This was done by cyclic loading of electropolished tensile specimens at different constant and changing potentials. Material investigated was a surgical implant steel X2CrNiMo18-15-3 which was immersed in physiological NaCl solution. Pitting and repassivation potentials were determined. Samples with and without artificial cracks as well as masked specimens were tested. Incubation period for first damage, density and size of pits by coulometric and volumetric method were determined. The fracture surfaces were then investigated by SEM. Results show that not in all cases pitting corrosion was the cause for corrosion fatigue cracking. Also pitting is favoured by crack formation. Density of pits increases by a factor of 5 without any change to pitting potential. There are primary pits formed prior to crack initiation and secondary pits formed after crack initiation. At samples without crack there is almost no difference between the optically measured value of total pit volume and the coulometrically determined value. At samples with cracks coulometric volume of pits is much larger than optical one. This proves that there is a significant amount of crevice corrosion in the crack. The corrosion current density in the crack increases by two orders of magnitude when comparing it to electropolished surface of the sample. Results of laboratory experiments are confirmed by failure of a real implant.     

316L不锈钢表面纳米化后腐蚀性能研究

对表面纳米化和未经表面纳米化处理的316L不锈钢的样品分别进行点蚀实验和应力腐蚀对比实验,在3.5%(质量分数)NaCl水溶液中分别测出它们的极化曲线.结果表明,316L不锈钢表面纳米化后抗点蚀性能下降,抗应力腐蚀性能提高.对应力腐蚀断口的SEM 分析发现,316L不锈钢应力腐蚀断口有明显分区现象,断裂形式为韧性断裂,开裂通道既有穿晶型也有沿晶型.     

铁氧化菌作用下316L不锈钢点蚀电化学特性的研究

采用电化学测量、交流阻抗技术、扫描电镜观察和能谱分析等实验方法,研究了316L不锈钢在铁氧化菌(IOB)溶液中的腐蚀电化学行为,分析了炼油厂冷却水系统微生物腐蚀的特征及机制,结果表明,在含有IOB溶液中的自腐蚀电位(Ecorr)、点蚀电位(Epit)和极化电阻(Rp)均随浸泡时间的增加呈现出降-升-降的变化趋势;在含有IOB溶液中的腐蚀速率均大于在无菌溶液中;IOB的生长代谢活动及其生物膜的完整性和致密性影响了316L不锈钢表面的腐蚀过程,使不锈钢表面的钝化膜层腐蚀破坏程度增加,加速了316L不锈钢的点蚀.     

特种设备用双相不锈钢抗点蚀性能研究

点蚀是不锈钢最有害的腐蚀形态之一,点蚀往往是应力腐蚀裂纹和腐蚀疲劳裂纹的起始部位。点蚀是一种腐蚀集中于表面的很小范围内,并深入到金属内部的腐蚀形态,一般形状为小孔状,其危害性比均匀腐蚀严重得多,会引起爆炸、火灾等事故。双相不锈钢兼有铁素体和奥氏体的特性,它将铁素体良好的强度、硬度和奥氏体优良的塑性和韧性结合起来,并具有优良的耐点蚀性能,无论是在力学性能上还是在耐腐蚀性上,双相不锈钢都明显优于铁素体不锈钢和奥氏体不锈钢,可以在点蚀环境中的特种设备上广泛使用。     

Pitting corrosion of a Rare Earth Mg alloy GW93

Pitting corrosion of magnesium(Mg) alloys is greatly associated with their microstructure, especially second phases. The second phases in traditional Mg alloys such as AZ91 are electrochemically nobler than Mg matrix, while the second phases in Rare earth(RE) Mg alloy GW93 are more active than Mg matrix. As a result, the pitting corrosion mechanism of Mg alloy GW93 is different from the traditional ones. This paper aims to clarify the pitting corrosion mechanism of Mg alloy GW93 through the studies of Volta potential by Scanning Kelvin Probe Force Microscopy(SKPFM), corrosion morphology by Scanning Electron Microscope(SEM), and corrosion resistance by electrochemical tests. Results reveal that the pitting corrosion of GW93 includes three stages, first, dissolution of the second phases, followed by corrosion of Mg matrix adjacent to the dissolved second phases, and finally, propagation of corrosion pits along the depth direction of the dissolved second phases. Anodic second phases and enrichment of Clin the thick corrosion product films dominate the propagation of pitting corrosion.