A new perspective on measuring the corrosion rate of localized corrosion

Many corrosion phenomena are nonuniform, which means that anodic and cathodic locations are spatially separated. An example is macrocell corrosion of steel in concrete. Under these conditions, determining the corrosion rate from polarization resistance measurements and using the Stern–Geary equation is fundamentally not possible. We present a novel theoretical approach for the interpretation of galvanostatic pulse measurements, to make them applicable as a method for corrosion rate measurements in situations of localized corrosion. Experiments show that it is important to consider that (a) only a fraction of the applied current flows through the anode of the macrocell, and (b) this current is not constant over time. We propose an approach to quantify and consider these two effects, based on information generally accessible in condition assessment of concrete structures. Our results show that galvanostatic pulse measurements are a robust method to determine the corrosion current. With the traditional empirical approach, the measurement error was generally below factor 3, and occasionally up to factor 10. With the novel approach, this error could be reduced to a factor of maximum 2 in all cases.     

海洋环境硫酸盐还原菌对金属材料腐蚀机理的研究进展

硫酸盐还原菌(SRB)是一类广泛存在于自然环境中可以利用硫酸盐类物质作为呼吸代谢电子受体的厌氧类微生物,是造成金属腐蚀破坏和设备故障的主要原因之一,已经成为一个重要的研究课题。由于微生物活动的复杂性,生物膜内SRB与金属表面的相互作用缺乏深入的研究,其诱导腐蚀机理和腐蚀过程尚不清楚,难以进行有效的腐蚀预测。基于此,本文从SRB生物膜的呼吸代谢角度介绍了其诱导金属腐蚀的研究进展。介绍了SRB的生态特征和厌氧呼吸过程,重点综述了SRB腐蚀机理,包括阴极去极化、代谢产物腐蚀、浓差电池作用和胞外电子传递等理论,最后简要介绍了微生物腐蚀(MIC)研究的方法与技术手段。     

Effect of palladium on the corrosion behavior of titanium

The effects of palladium (Pd) additions on the localized and uniform corrosion of titanium (Ti) were examined by comparing the corrosion behavior of Ti Grade 2 (UNS R50400) to that of Pd-bearing Ti Grade 7 (UNS R52400). Pd additions were found to increase the pitting (E_pit) and repassivation (E_rp) potentials such that E_pit for Ti Grade 2 was significantly lower than E_rp for Grade 7 in chloride (Cl⁻) solutions. The effect of Pd on Ti can be explained through the effects Pd has on the hydrogen evolution reaction. Though Pd additions did significantly affect the localized corrosion resistance of Ti, Pd did not appear to influence the passive corrosion rate nor did it mitigate the deleterious effects of fluoride (F⁻). Fluoride was found to dramatically increase the measured corrosion current above a critical concentration of about 0.5 mM.     

醇胺类化合物对混凝土钢筋的阻锈作用研究

本文研究了醇胺类化合物对混凝土钢筋的阻锈作用。利用静态失重法、极化曲线等方法,在与传统缓蚀剂亚硝酸钠对照的基础上,检测和评价乙二醇和乙醇胺两种醇胺类有机缓蚀剂,对钢筋在含有NaCl的模拟混凝土孔溶液中的电化学腐蚀行为及其阻锈作用。极化曲线图表明模拟混凝土孔溶液pH=11．5和加入缓蚀剂浓度为3％（与孔溶液的体积比）时,醇胺类缓蚀剂对钢筋阻锈效果最好,钝化电位为940mV;静态失重法表明缓蚀剂为水泥重量的3％是防止混凝土钢筋发生点蚀最适宜的浓度,此时缓蚀率达94％;实验同时发现在以上条件下乙醇胺的缓蚀作用与亚硝酸钠相当,且乙醇胺与其它缓蚀剂有良好协同效应,能明显增强其对钢筋的阻锈能力。     

加速腐蚀实验研究碳钢的大气腐蚀行为

目的快速研究大气环境对钢制输电铁塔腐蚀的影响。方法采用室内加速腐蚀实验,研究碳钢试样在湿度和SO2浓度不同的气氛中的腐蚀行为。结果用极化曲线法测得的金属腐蚀速率与失重法测得的结果具有很高的一致性。相对湿度较低时,改变腐蚀性气体的浓度,对碳钢的腐蚀影响不显著;碳钢在高湿度的含SO2气氛中会发生严重腐蚀。结论降低湿度是防止或减缓碳钢在含SO2气氛中腐蚀的有效途径。     

Properties and effects of water-soluble inhibitors on the corrosion rates of structural metals

The effects of six commercial water-soluble inhibitor formulations on the corrosion rates of aluminum and steel in seawater were determined. Corrosion rates were measured by the weight loss of specimens following long-term immersion in artificial seawater containing inhibitors at the developer’s recommended dosages. The effects of environmental changes on inhibitor behavior were also investigated by varying the seawater concentration in certain tests. Surface plasmon resonance (SPR) spectroscopy was investigated as a method to observe the inherent adherence and persistence of the inhibitors at a metal surface. Results show that the level of effectiveness of the test inhibitors varies significantly and is dependent on the nature of the metal being protected. While some inhibitors reduce the corrosion of steel by up to 80%, others actually increase the corrosion rate. Four of the six inhibitors were observed to increase aluminum pitting; the other two offered protection. Two of the inhibitors reduced the corrosion rates for the aluminum and steel. Surface plasmon resonance spectroscopy was able to detect and discriminate between inhibitors. These measurements show good correlation between the adherence of an inhibitor to a metal surface and its ability to reduce corrosion rates. Results of this study provide a firm measure of the levels of corrosion control that can be achieved by commercially available inhibitor formulations. They also provide a quantitative basis for comparison and selection of corrosion inhibitors for use in a variety of applications (i.e., metal holding tanks and cans, recirculation loops, and modified wash downs of outdoor equipment typically experiencing deterioration due to exposure to salt-containing environments).     

分流塔套筒焊缝应力腐蚀开裂分析

通过对断口形貌的金相、SEM、XRD检测分析，确定了Q235、TZ33钢制套筒焊缝处出现的裂纹为应力腐蚀裂纹。焊缝开裂的主要介质因素是CO2，在100～110℃的使用温度下CO2浓度偏高，以及焊后残余应力和工作应力的叠加，促进了应力腐蚀开裂。并根据分析结果提出了套筒制造工艺的改进措施。     

Ni-Cr-Mo-Cu合金耐晶间腐蚀及点蚀性能研究

在Cr、Mo成分一定的情况下,通过改变铜的质量分数(1％～5％),制备新型Ni-Cr-Mo-Cu耐蚀合金.利用化学浸泡法、电化学法(极化曲线法、循环伏安法)对其耐晶间腐蚀以及耐点蚀能力进行分析研究.实验结果表明,w(cu)=1％～5％的Ni-Cr-Mo-Cu合金具有优良的耐晶间腐蚀以及点蚀性能,相对而言w(cu)=2％的镍基合金耐晶间腐蚀以及点蚀性能较差,因此说明合适的铜含量可以提高镍基合金的耐晶间腐蚀和点蚀性能;并且试验合金晶间腐蚀与点蚀的电化学行为和特征与其浸泡腐蚀的结果是吻合的.     

原油高温腐蚀性能研究

本文综述了国内外原油高温腐蚀性能的研发现状,分别归纳分析了高温硫腐蚀和高温环烷酸腐蚀在腐蚀机理及其影响因素、腐蚀预测、以及腐蚀控制措施方面的研究进展。同时探讨了存在的问题和可能的重点研究方向。     

The effect of applied tensile stress on the exfoliation corrosion of 7075‐T6 alloy

The effect of the applied tensile stress on the exfoliation corrosion of 7075‐T6 alloy in EXCO solution has been studied. Electrochemistry Impedance Spectroscopy (EIS), Scanning Electron Microscope (SEM) and optical microscope techniques were used to characterize the initiation and propagation of the exfoliation corrosion (EC) under different applied tensile stress levels. Two equivalent circuit models were developed to fit the EIS data of the initiation and propagation stages of EC according to their corresponding physicochemical properties respectively. The correlation between the characteristics of EIS evolution and the localized corrosion types was established, and a new criteria for detecting the initiation of EC of aluminum alloys was brought forward. The results also showed that the tensile stress accelerates EC by increasing the number of the active sites during its initiation stage.     

西南地区某输油管道外腐蚀分析

目的研究西南地区某输油管道外腐蚀行为。方法现场检测,对土壤理化性质及腐蚀产物成分进行室内分析。结果开挖点A的土壤呈弱碱性,土壤腐蚀性弱,管道发生轻微均匀腐蚀,腐蚀产物主要为FeO(OH),Fe(OH)3和Fe3O4等铁的氧化物,对应的阴极反应为吸氧反应;开挖点B的土壤酸性强,硫酸根离子浓度高,土壤腐蚀性强,管道发生严重坑蚀,腐蚀产物主要成分为FeSO4·7H2O及少量碱式硫酸铁,对应的阴极反应以析氢反应为主。结论开挖点土壤的理化性质差异,导致管道的腐蚀形态、腐蚀产物和腐蚀机理显著不同。     

温度对三种Cr钢腐蚀行为的影响

利用高温高压釜模拟油田高CO_2分压和高矿化度的生产环境进行腐蚀试验,测定在不同温度条件下1Cr、3Cr和13Cr钢的腐蚀速率,利用扫描电镜(SEM)、X射线衍射仪(XRD)等手段分析了腐蚀产物形貌和成分。结果表明:1Cr、3Cr钢的腐蚀速率随温度升高先增大后减小,二者的腐蚀速率均在80℃达到最大值,分别为7.515mm/a和4.339mm/a;13Cr钢的腐蚀速率在温度低于110℃时随温度的升高缓慢增大,在温度高于110℃时腐蚀速率迅速增大;1Cr、3Cr油管钢在试验温度范围内均出现局部腐蚀,13Cr油管钢在整个试验的温度区间表现出优秀的耐蚀性。     

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 针对某炼铁高炉1Cr18Ni9Ti材质的炉顶布料溜槽局部损坏,采用光学显微镜及扫描电子显微镜等设备解剖分析了承力外壳的损坏特征及其原因。分析结果认为：应力腐蚀和晶间腐蚀的共同作用是溜槽承力外壳锈蚀、减薄、开裂的主要原因。     

含硫代硫酸根铝酸钠溶液中时间 对Q345钢腐蚀的影响

目的 在含4 g/L S2O32?的铝酸钠溶液中,研究腐蚀时间对Q345钢腐蚀行为的影响,探索腐蚀规律,明确腐蚀机理。方法 采用盐雾腐蚀和电化学腐蚀实验,通过腐蚀失重法、极化曲线、阻抗谱、SEM、EDS等手段,研究Q345钢的腐蚀行为。结果 当腐蚀时间从3 d延长至7 d时,腐蚀失重从2.4505 g/m2增大至2.6420 g/m2,点蚀深度从3.3 μm升高至4.6 μm,超过7 d以后,趋于稳定。腐蚀速率方程为V =2.426t?0.975,1~3 d范围内,腐蚀速率急剧下降。初期腐蚀电流密度较大,由3 d增至5 d时,腐蚀电流密度由6.538 μA/cm2迅速降低至0.785 μA/cm2,之后逐渐降低至0.308 μA/cm2（9 d）,容抗半径和电荷转移电阻Rct均随腐蚀时间的增加而增加。腐蚀时间延长,产物中O、Al、S等元素的含量增加,Fe元素含量降低。结论 腐蚀初期,OH?优先吸附,生成较致密的Fe3O4与FeOOH;腐蚀中期,S2O32?与基体反应形成粘附力弱的FeS,使得Fe3O4结构不稳定而脱落,产物结构疏松;腐蚀后期,Al(OH)3转变为Al2O3,AlO2?与Fe3O4形成尖晶石FeAl2O4,结构较为致密,覆盖基体表面,阻碍了腐蚀介质与基体的接触,腐蚀速率降低。     

铜镍合金BFe30-1-1在NaCl溶液中的腐蚀行为

对铜镍合金BFe30-1-1在NaCl溶液中的腐蚀行为进行了研究.测其在不同pH值的0.5mol/L NaCl溶液中的阳极极化曲线,并选择在一定电化学条件下进行恒电位腐蚀.通过对腐蚀后溶液中的Cu2 和Ni2 含量的分析和对试样断面的微区成分分析,从而了解不同条件下的铜镍合金的选择性腐蚀规律.实验结果表明:铜镍合金BFe30-1-1的选择性腐蚀类型取决于腐蚀介质的酸碱度及腐蚀电位等电化学条件.     

Effects of fuel impurities on the fireside corrosion of boiler tubes in advanced power generating systems—a thermodynamic calculation of deposit chemistry

Thermodynamic equilibrium calculation relating fuel chemistry with flue-gas composition and volatile condensate deposits on tube metals upon combustion of various “dirty” fuel was conducted for a better understanding of the deposit chemistry of superheater tubes in steam-generating boilers. Corrosive impurities such as sodium, potassium, chlorine, and sulfur, inevitably involved in fuel, were considered in the calculation. Possible influence of flue-gas temperature on deposit chemistry was investigated as well.Based on the flue-gas composition and the deposit chemistry, corrosion environments of steam-generating boilers firing various “dirty” fuel were discussed.     

低比例甲醇汽油对金属的腐蚀研究

目的减轻甲醇汽油的腐蚀性。方法以汽车油路系统常用的紫铜、黄铜、钢、铁、铝等金属材质为研究对象,采用金属试片的腐蚀度和颜色变化相结合的方法,分析判断甲醇汽油的腐蚀性,通过考察不同金属试片在不同含量甲醇汽油、含水甲醇汽油以及添加缓蚀剂甲醇汽油中的腐蚀情况,分析甲醇汽油腐蚀的主要原因,并根据缓蚀机理筛选缓蚀剂。结果低比例甲醇汽油对不同金属材质都有明显的腐蚀作用,与93#汽油相比,加入5%(体积分数)的甲醇就能使紫铜、黄铜、钢、铝的腐蚀度增加一倍以上。少量水分可加剧甲醇汽油的腐蚀,但当水含量达到一定程度时,腐蚀度减小。缓蚀剂B对铜系金属材质的腐蚀有较好的抑制作用,缓蚀剂C对铁片腐蚀有较好的抑制作用,复配缓蚀剂H对所选金属材质都有良好的缓蚀效果,可使紫铜、黄铜、铁和铝的缓蚀率分别减小82.1%、81.5%、85.3%和89.5%。结论复配的缓蚀剂能够有效地减缓甲醇汽油对金属的腐蚀。     

宝浪油田土壤腐蚀性评价研究

通过对宝浪油田不同区块土壤理化性质的测定及土壤腐蚀埋片试验,评价出宝浪油田不同区块土壤的腐蚀等级,为宝浪油田埋地管线防腐设计提供了理论依据。