稀土铝黄铜合金在NaCl+NH4Cl腐蚀液中的腐蚀行为

利用失重法、X射线衍射分析、扫描电镜与能谱分析等手段研究了Cu-Zn-Al-Ni-B-Ce合金在自来水和去离子水配置的NaCl(35g/L)+NH4Cl(26.75g/L)腐蚀液中的耐腐蚀性能及其腐蚀行为。结果表明:该合金在溶液中的腐蚀产物均主要为稀土氧化物(Ce4O7)、铜的碱式氯化物(Cu(OH)Cl)和铜氨络合物的水合物(Cu(OH)2NH3.H2O);在去离子水溶液中合金的腐蚀速率为1.60×10-3mm/a,在自来水溶液中的腐蚀速率达到了7.51×10-2mm/a;合金在两种腐蚀液中均有沿晶界腐蚀现象,合金在自来水溶液中的腐蚀产物厚度10~20μm,远大于合金在去离子水中的腐蚀产物厚度1μm左右,且经去离子水溶液腐蚀后的合金表面比经自来水溶液腐蚀后的平滑。     

热浸镀镍基合金涂层组织及腐蚀行为

采用热浸镀技术在Q235钢表面制备了镍基合金涂层,采用XRD和SEM-EDS研究了涂层腐蚀前后的相组成、形貌和成分,并探讨了腐蚀机理.结果表明:涂层中有多种形态的析出物,涂层与基体之间存在宽5～8μm的过渡带;盐雾试验后,涂层表面腐蚀产物为Ni(OH)2,Fe3O4和Fe+3O(OH),平均腐蚀速率大约为1.18×10-7g/(h·mm2);腐蚀首先发生在显微孔洞或析出相边界处,表现为局部腐蚀特征.     

炉水温度影响碳钢腐蚀的试验研究

通过高压釜挂片试验 ,研究了在不同温度的模拟炉水中碳钢的腐蚀 ,采用计算腐蚀增重速率、腐蚀产物电子探针微区元素分析、表面形貌分析 ,溶液中总铁离子浓度的测定及表面物相的X衍射分析等研究方法 ,结果表明 :碳钢的腐蚀速率随温度的升高而增加 ,在低温区 (15 0～ 2 0 0℃ ) ,铁的氧化速率小于溶解速率 ,在高温区 (2 5 0～ 36 0℃ ) ,铁的氧化速率大于溶解速率 ,在 2 0 0～ 2 5 0℃有一过渡区域。动力学近似计算碳钢在水临界点附近的腐蚀速率约为 0 .10 g/h·m2 ,与试验结果相符合     

NaCl薄液膜下不锈钢腐蚀行为研究

利用Kelvin探针参比电极技术和电化学阻抗方法研究了不锈钢在不同厚度NaCl薄液膜下的腐蚀行为.结果表明:在0.35%NaCl液膜厚度7～90 μm范围内,随着液层厚度的增大,不锈钢在薄液膜下腐蚀的氧扩散控制特征越显著,而且氧还原反应极限电流逐渐降低;3.5%NaCl薄液膜下阻抗测得的溶液电阻随着液膜增厚而首先迅速降低然后趋于平稳;在液层较厚时(425～120 μm)随着液层厚度的减小,腐蚀速度受氧扩散控制逐渐增大;液层厚度减薄至40～120 μm区间,由于阳极反应受抑制和阴极反应加速的共同影响腐蚀速度会出现极小值;液层厚度非常薄(20 μm以下)时由于电流分布不均匀抑制了氧还原,腐蚀速度很低.     

不同镍基堆焊材料在高温高压水中的应力腐蚀行为研究

通过U弯浸泡实验研究了电渣焊600合金、电渣焊690合金和埋弧焊690合金三种材料的应力腐蚀行为。研究结果表明:模拟压水堆核电站一回路水化学工况,温度为325℃,压力为15.8 MPa,溶液中含1.5×10~(-3)B、2.3×10~(-6)Li、2.5×10~(-6)H_2,浸泡1193 h后,电渣焊600合金、电渣焊690合金和埋弧焊690合金样品均未发生应力腐蚀开裂。在温度为330℃,压力为11 MPa,含10 mass%NaOH的高温高压强碱溶液中,电渣焊600合金样品浸泡720 h后发生了应力腐蚀开裂,最大裂纹长度为835μm;浸泡1440 h后,裂纹进一步扩展,达到1135μm,具有典型的沿晶应力腐蚀开裂(IGSCC)特征;电渣焊690合金样品经过1440h浸泡后,表面萌生长度为0.3μm到1.15μm不等的微裂纹;埋弧焊690合金样品经过1440 h浸泡后未发生应力腐蚀开裂。     

等径角挤压制备的超细晶Al-5%Cu合金块材的腐蚀行为

采用全浸泡腐蚀和电化学腐蚀研究等径角挤压制备的超细晶铝铜合金块材在氯化钠溶液中的腐蚀行为。结果表明:超细晶铝铜合金中基体相α(Al)晶粒细小(为200～300nm);铸态组织中网状θ相(Al2Cu)破碎、细化成10μm左右的颗粒并均匀分布于形变α(Al)基体上;形变细化提高铝铜合金在氯化钠介质中的耐蚀性能,表现出全浸泡腐蚀中更轻的腐蚀程度、电化学测试中更大的极化电阻、更正的自腐蚀电位和点蚀电位、更小的腐蚀电流密度。     

固溶时间对Mg-2Zn-1Y-0.5Zr合金组织与腐蚀性能的影响

通过光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)、浸泡测试和电化学测试等研究了Mg-2Zn-1Y-0.5Zr合金在490℃固溶4～14h后的微观组织和腐蚀性能.结果 表明:随着固溶时间的延长,合金的晶粒尺寸逐渐由98.19 μm增大到142.90 μm,合金中的第二相逐渐溶解,第二相体积分数由1.33％降到0.02％,大幅降低了第二相与合金基体之间因腐蚀电位不同而引起的微电偶腐蚀;在490℃固溶处理8h时后,合金的腐蚀速率为0.414 mm/y,自腐蚀电位为-1.525 V,自腐蚀电流密度为3.327 μA/cm2,耐蚀性能最好.     

SO2存在下NaCl沉积量对Zn大气腐蚀的影响

用石英晶体微天平研究了不同沉积量的NaCl在SO2质量分数为1×10-6时对Zn大气腐蚀的影响,分析了该条件下Zn初期大气腐蚀的规律.结果表明,Zn的腐蚀增重随NaCl沉积量的增加而增加,它们之间有着较好的线性关系NaCl沉积量较高时,暴露一段时间后,Zn的大气腐蚀有减弱的趋势.建立了反映其腐蚀及影响因素的经验方程△m/A=K(t/ttot)b.采用X射线衍射(XRD)和显微红外技术(IR)对Zn表面腐蚀产物进行了分析.     

夹杂物对易切削钢曲轴耐酸蚀性能的影响

使用金相显微镜、扫描电镜、能谱分析仪等研究了MnS夹杂物对感应淬火易切削钢曲轴表面耐酸蚀性能的影响。结果表明:在10%(体积分数)硝酸水溶液中,裸露在曲轴表面的MnS夹杂物可促使MnS夹杂物/金属基体界面作为形核质点诱发点蚀,MnS夹杂物阳极氧化反应产物促使其附近微区内进一步发生强烈的氧化腐蚀,以腐蚀坑的形式破坏曲轴基体表面完整性。数据统计分析表明腐蚀坑最大宽度集中在30～55μm,最大深度度集中在10～25μm。     

不同晶粒尺寸5083铝合金晶间腐蚀和应力腐蚀开裂的差异性

通过冷轧和退火获得具有不同晶粒尺寸(8.7～79.2μm)的5083铝合金板.研究其微观结构、晶间腐蚀(IGC)、应力腐蚀开裂(SCC)和裂纹扩展行为.结果表明,粗晶粒样品表现出更好的抗IGC性能,其腐蚀深度为15μm.慢应变速率测试结果表明,细晶粒样品表现出更好的抗SCC性能,敏感性指数ISSRT为11.2％.此外,...     

A study of the corrosion of aluminum alloy 2024-T3 under thin electrolyte layers

The corrosion of aluminum alloy 2024-T3 (AA2024-T3) under thin electrolyte layers was studied in 3.0 wt% sodium chloride solutions by cathodic polarization and electrochemical impedance spectroscopy (EIS) method. The cathodic polarization measurements show that, when the electrolyte layer is thicker than 200 μm, the oxygen reduction current is close to that of the bulk solution. But in the range of 200-100 μm, the oxygen reduction current is inversely proportional to the layer thickness, which shows that the oxygen diffusion through the electrolyte layer is the rate-determining step for the oxygen reduction process. In the range of 100 μm to about 58 μm, the oxygen reduction current is slightly decreased probably due to the formation of aluminum hydroxide or the change of the diffusion pattern from 2-dimensional diffusion to one-dimensional diffusion. The further decrease in electrolyte layer thickness increase the oxygen reduction current to some extent again, because the diffusion of oxygen plays more important role in thin electrolyte layers.The EIS measurements show that the corrosion is controlled by the cathodic oxygen reduction at the initial stage, showing the largest corrosion rate at the electrolyte layer thickness of 105 μm. But at the later stage of corrosion, the anodic process begin to affect the corrosion rates and the corrosion rates show a maximum at 170 μm, which may be the thickness where the corrosion changes from cathodic control to anodic control. The corrosion rate under the very thin electrolyte layer (62 μm in this study) is even smaller than that in bulk solution, this is due to that the anodic process is strongly inhibited.     

On size effect of rate of corrosion of copper nanowire ensemble: Part 2. Size effect of rate of corrosion of copper in pyrophosphate solution

The corrosion of specimens of copper produced by electroplating on disc electrodes 10–500 μm in diameter from a pyrophosphate electrolyte is studied in this electrolyte (without added copper ions) using polarization curve measurements. It is found that the rate of corrosion of the microelectrodes with a radius of 5 μm is eight times higher than that of the microelectrodes with a radius of 25 μm; the measured rate of corrosion remains unchanged when varying the radius of the microelectrode in a range of 25–250 μm. It is shown that the process under investigation is corrosion with oxygen depolarization; the rate of reduction (of dissolved oxygen) increases eightfold when varying the radius of the microelectrode in a range of 5–25 μm. The experimental results are confirmed by the calculations of diffusion currents for the microelectrodes, which show that the size effect, i.e., an increase in the diffusion current density with decreasing area of the electrode surface, should be observed for electrodes with a radius less than 20–30 μm.     

Microstructure and corrosion resistance of modified 2024 Al alloy using surface mechanical attrition treatment combined with microarc oxidation process

A top ceramic coating was fabricated on the surface mechanical attrition treatment (SMAT) modified nanocrystalline layer of 2024 Al alloy by microarc oxidation (MAO) process. The corrosion resistance of the SMAT-MAO composite coating was studied by EIS. The results show that SMAT-MAO composite coating with 10 μm top ceramic coating exhibited better corrosion resistance, while the SMAT-MAO coating with the thickness of 15 μm showed worse corrosion resistance compared with those simple MAO coatings with same thickness. The formation of a dense passive film at the damaged region caused by the bottom nanocrystalline interface contributed to the improved corrosion resistance property.     

Reaktionen zwischen Natriumpolysulfid und Stromabnehmermaterialien für Natrium/Schwefel-Batterien

Reactions between sodium polysulfide and materials for current feeds in sodium-sulfur batteries In order to measure corrosion rates of potential materials for current feeds in the sodium polysulfide melt of sodium-sulfur batteries changes with time of the thicknesses of thin films were measured using the 4-point resistance method. At the free corrosion potential the steady state corrosion rate of aluminium in Na₂S₄ at 350°C was ? 150 μm/a and the activation enthalpy around 300 kJ/mol. At sufficiently high cathodic currents the corrosion rates were observed to increase linearly with the square of the total current. Upon anodic polarisation the thickness of the passivating film was increased, but there was not much influence on the mean corrosion rate. However, there were indications of local differences of the corrosion rate. The steel X10CrA124 corroded by growth of a film according to the parabolic rate law until a steady state corrosion rate was attained being 90 μm/a at 350°C. The steel X10CrNiMoTi 18 10 not containing aluminium corroded at the rate of 1.5 mm/a. The corrosion rate of chromium was even higher. On the other hand, Stellite 6 and glassy carbon corroded at rates < 2 μm/a.     

应用电化学方法原位研究薄液膜下青铜的大气腐蚀行为(英文)

采用阴极极化曲线、开路电位和电化学阻抗谱,监测青铜在不同薄液膜厚度下的大气腐蚀行为。阴极极化曲线结果表明,阴极极限电流密度随着液膜的减薄而增大。电化学阻抗谱结果表明,在腐蚀初期,腐蚀速率随着液膜的减薄而增加,这主要是由于腐蚀速率是由阴极过程控制的;随着时间的延长,腐蚀程度随着液膜厚度的变化从强到弱的趋势为:150μm,310μm,100μm,本体溶液,57μm。开路电位和电化学阻抗谱实验较好地再现了原位电化学腐蚀信息,且电化学结果与物理表征具有良好的一致性。     

TAMZ合金在人工唾液中的电化学行为

运用电化学方法对工业纯Ti，Ti6Al4V合金和TAMZ合金在人工唾液中的电化学行为进行了研究，探讨了溶液pH值对Ti合金电化学性能的影响。结果表明，在人工唾液中，TAMZ合金具有最佳电化学稳定性，腐蚀速率最低。Ti合金在人工唾液中存在较大的钝化区间，电化学稳定性按工业纯Ti，Ti6Al4V合金和TAMZ合金的顺序依次增强。随溶液pH值升高，试样的热力学稳定性增强。交流阻抗结果显示，3种实验材料在人工唾液中具有优异的耐蚀性能，腐蚀速率均在10^-2μm／a数量级，小于医用级标准0．25μm／a。     

Influences of NH4 + ions and thin electrolyte layers (TEL) thickness on the corrosion behavior of AZ91D magnesium alloy

In this study, the influences of NH₄ ⁺ ions and the thin electrolyte layer (TEL) thickness on the corrosion behavior of the AZ9D magnesium alloy in NH₄⁺‐containing environments were investigated by electrochemical measurements and surface characterization. The experimental results indicate that NH₄⁺ greatly accelerates the corrosion of AZ91D magnesium alloy whether in a bulk solution or in a TEL. As the TEL thickness decreasing, the corrosion resistance of the AZ91D magnesium alloy is strengthened. According to the corrosion morphology, electrochemical analysis, and characterization analysis of corrosion products, the corrosion mechanism of AZ91D under TELs with different thicknesses is divided into three stages: (a) uniformly distributed corrosion pits with deep depth and large size when TEL thickness is higher than or equal to 500 μm; (b) slightly corrosion with randomly distributed corrosion pits and the accumulation of small amount of corrosion product when TEL thickness is between 100 μm and 200 μm; (c) no corrosion pit with only deposition of corrosion product when TEL thickness is lower than or equal to 100 μm. Among which, the roles of NH₄⁺, TEL thickness, and corrosion product are emphasized and discussed in the corrosion process of AZ91D magnesium alloy under TEL with different thicknesses.     

Plasma post oxidation of nitrocarburized AISI 4140 steel

Plasma nitrocarburizing and plasma oxidizing treatments were performed to improve the wear and corrosion resistance of AISI 4140 steel.Plasma nitrocarburizing was conducted for 3 h at 570 ℃ in the nitrogen, hydrogen and methane atmosphere to produce the ε-Fe2-3(N,C) phase.It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of ε-phase, with a small proportion of γ'-Fe4(N,C) phase.The thickness of the compound layer was about 10 μm and the diffusion layer was about 300 μm in thickness, respectively.Plasma post oxidation was performed on the nitrocarburized samples with various oxygen/hydrogen ratio at a constant temperature of 500 ℃ for 1 h.The very thin magnetite (Fe3O4) layer 1-2 μm in thickness on top of the compound layer was obtained by plasma post oxidation.It was confirmed that the corrosion characteristics of the nitrocarburized compound layer can be further improved by the application of the superficial magnetite layer.     

Potential of biocorrosion in Danish district heatings sytems

Danish district heating (DH) systems utilise water with unique characteristics that include low conductivity, high pH, nutrient poor and anaerobic (oxygen free) conditions in order to reduce corrosion rates. This survey was carried out in order to investigate the potential for biofilm formation and biocorrosion in these systems. Determination of total bacterial numbers in water samples were performed in 29 DH systems and showed a range of 10²–10⁵ cells · ml^?1. The potential for biofilm growth was further examined in corrosion monitoring units located at 6 DH locations. Total bacterial numbers in biofilm on mild steel were found in the range of 10⁴–10⁶ cells · cm^?2. The mild steel coupons were examined for general corrosion rates based on weight loss together with an investigation of pitting corrosion. The general corrosion rates were up to 12 μm · year^?1, while the pitting analysis showed pit depths up to 90 μm for half a year of exposure. Presence of sulphate reducing bacteria (SRB) was found in all systems tested with corrosion monitoring units, whereas sulphide was found to different extents in the biofilms on all mild steel coupons. It was shown that DH systems with the highest number of bacteria in the biofilm generally had the most pronounced corrosion. The results show that despite the nutrient poor environment in the DH systems the potential for biofilm formation and biocorrosion was present.     

集输管线硫酸盐还原菌诱导生物矿化作用调查

利用扫描电镜 (SEM)、能谱、X射线衍射仪 (XRD) 和超景深三维立体显微镜等表面分析手段,调查研究油田污水集输管线材料的腐蚀和结垢行为。实验结果表明,暴露在没有添加杀菌剂的污水中30 d的试样表面形成了大量的垢状沉淀物,局部放大可以发现以胞外聚合物为主的生物膜覆盖在试样表面,此时生物膜的厚度高达169.6 μm,生物膜中含碳酸盐垢和细菌代谢产物硫铁化合物,且膜下基体材料局部腐蚀孔深度达到23.96 μm。在连续添加100 mg/L有机胍类杀菌剂1个月后,试样表面覆盖物中以无机矿物为主,且膜层厚度较未添加的薄,厚度为48.6 μm,膜下腐蚀较均匀,局部腐蚀轻微。硫酸盐还原菌参与的生物作用是管线局部腐蚀穿孔的主要原因之一。