碳钢/钛合金复合材料在3%NaCl溶液中的电偶腐蚀研究

采用失重方法和电化学方法,研究碳钢/钛合金复合材料在3%NaC l溶液中的电偶腐蚀行为。结果表明,在碳钢/钛合金电偶腐蚀过程中,碳钢为阳极,钛合金为阴极,随着阴/阳面积比的增大,电偶电流增大,碳钢腐蚀速率变大,而电偶电位基本不变。     

Polarization and impedance studies on zinc phosphate coating developed using galvanic coupling

Galvanic coupling technique is capable of producing coatings of desired thickness. Good quality coatings can be produced at low temperature. Galvanic coupling of mild steel (MS) with the other cathode materials such as titanium (Ti), copper (Cu), brass (BR), nickel (Ni), and stainless steel (SS) accelerates iron dissolution, enables quicker consumption of free phosphoric acid and facilitates an earlier attainment of point of incipient precipitation, resulting in a higher amount of coating formation. In the present investigation, potentiodynamic polarization and electrochemical impedance spectra on MS substrates phosphated using galvanic coupling are studied. This study reveals that MS substrates phosphated under galvanically coupled condition possess better corrosion resistance than the substrates phosphated under uncoupled condition.     

Theoretical and experimental study of galvanic coupling effects between carbon steel and stainless steels

The use of stainless steel in high corrosion risk areas represents a viable option for reducing the life-cycle cost and extending the service life of concrete structures. However, the possible galvanic corrosion between it and carbon steel continues to be a concern. In this article, the galvanic coupling behaviours of carbon steel and three different stainless steels were investigated in simulated pore solutions and concrete specimens. The results showed that the oxygen reduction reaction was much lower on stainless steel than on passive carbon steel, leading to a lower galvanic coupling current between stainless steel and corroding carbon steel than that between passive and corroding carbon steels. However, rust contamination of stainless steel was found to increase galvanic coupling corrosion on carbon steel.     

Carbon-induced corrosion of MSF condenser tubes in Arabian Gulf water

The present investigation was undertaken to shed light on the failure of some 90/10 CuNi condenser tubes in a MSF distiller. The tubes showed numerous tiny pits of unusual features. Particles of C were discovered inside the tubes and were suspected of initiating micro-galvanic cells leading to pitting. The study involved the measurement of open circuit potentials (OCP) of C and 90/10 and 70/30 CuNi electrodes in stagnant-, stirred-, natural- and synthetic seawaters at various temperatures. The way these changed with time till constant values were recorded was followed over long exposure times. The EMF of the C/CuNi galvanic cells varied between 400 and 450 mV. Contact between C and the copper alloys resulted in dissolution of copper, and the development of galvanic corrosion potentials and galvanic corrosion currents. These were discussed in the light of Evans corrosion diagrams. The study was extended to include the C/316 stainless steel system under similar conditions. The OCP behaviour of the steel electrode depended upon whether measurements were carried out in stagnant-, stirred-, natural- or synthetic seawaters. Galvanic coupling with C resulted in intensified pitting attack of steel in stagnant, artificial seawater. Similar measurements were conducted on the C/Ti couple. The anode reaction led to the thickening of TiO, Insignificant corrosion was recorded with the Ti/316 stainless steel system.     

Galvanic corrosion in the systems titanium/316 L stainless steel/Al brass in Arabian Gulf water

The present study aims to further the understanding of the galvanic corrosion behaviour of the two systems: titanium/Al brass and 316L stainless steel (st.st)/Al brass in Arabian Gulf water. The study involves the measuring of the open circuit potentials (OCP) of coupons of three metals in seawater at temperatures between 25°C and 65°C. When steady values are attained, the coupons are short-circuited and the couple potentials are followed as functions of time. Corrosion currents are simultaneously recorded. The OCP behaviour of each element depends on the prevailing experimental conditions. With Ti in stagnant and stirred solutions at all temperatures, the OCP shifts towards positive values denoting film formation, repair and thickening. Stainless steel in stagnant seawater at low temperatures undergoes pitting corrosion. At high temperatures the metal is protected by a film of CaCO₃, whereas in stirred solutions the metal escapes pitting. Peculiar behaviour is recorded, when together with the steel, a coupon of uncoupled Al brass is immersed in the same solution. This arrangement seems to protect against pitting attack. The OCP behaviour of Al brass in low-temperature seawater suggests film destruction and dissolution. Coupling of Ti or stainless steel to Al brass produces initial potentials near those of the base metal. At advanced times partial protection due to the electrochemical formation of CaCO₃ takes place. This affects the magnitude of corrosion currents which decrease also with a rise in temperature. These conditions are supported by the results of measurements carried out in synthetic seawater free from HCO₃ and Ca²⁺ ions. Because of the large difference between the free corrosion potentials of titanium and stainless steel, on the one hand, and of Al brass on the other, severe corrosion of the latter can occur. The intensity of attack can be greatly reduced when the oxygen content of the brine is reduced. The same can be achieved through the appropriate manipulation of the naturally forming CaCO₃ film.     

Development of a galvanic sensor system for detecting the corrosion damage of the steel embedded in concrete structures: Part 1. Laboratory tests to correlate galvanic current with actual damage

The correlation between sensor output and corrosion rate of reinforcing steel was evaluated by laboratory electrochemical tests in saturated Ca(OH)₂ with 3.5 wt.% NaCl. In this paper, two types of electrochemical probes were developed: galvanic cells containing of steel/copper and steel/stainless steel couples. The corrosion behavior in saturated Ca(OH)₂ solution with and without 3.5 wt.% NaCl addition for the different electrodes was investigated by potentiodynamic test. Weight loss measurement and galvanic corrosion test were conducted to obtain the corrosion rate of reinforcing steel and the charge of sensor in saturated Ca(OH)₂ solution with 3.5 wt.% NaCl addition, respectively.

The results of the potentiodynamic test indicated the possibility of detecting an ingress point of chlorides by measuring the galvanic current. In galvanic corrosion tests, the galvanic current of steel/copper couple was higher than that of steel/stainless steel couple, i.e., the steel/copper sensor is more suitable for high resistance environment. The steel/stainless sensor showed a better linear correlation than the steel/copper sensor. Through the relationship between the sensor system output and the weight loss (mg/cm²) of steel, real corrosion damage of the steel embedded in concrete can be detected.     

几种金属材料在乳酸中的腐蚀性能研究

采用失重法对316L不锈钢、Ti、Ni 3种材料在不同条件下的耐乳酸腐蚀行为进行了研究,详细考察了反应温度和反应时间对316L腐蚀的影响。结果表明,316L在L-乳酸中腐蚀速率随反应温度的升高而增大,在反应时间36 h,反应温度90℃和120℃下,腐蚀速率分别为0.382 mm/a和0.801 3 mm/a,属尚耐腐蚀;150℃和180℃下腐蚀速率分别为3.85 mm/a和6.01 mm/a,属不耐腐蚀。金相显微镜分析表明,316L不锈钢表面在较低温度的乳酸中以点蚀为主。现场挂片腐蚀实验结果表明,当温度低于120℃,316L可以作为乳酸生产设备的选材。     

Electrochemical behaviour of graphite-epoxy composite materials (GECM) in aqueous salt solutions

The electrochemical behaviour of graphite-epoxy composite materials (GECM) in neutral 3.5% aqueous solutions of NaCl has been investigated. Two types of composite and pure graphite have been studied. The composite material shows a high value of electrode potential ranging between –40 and +70 mV versus SCE, and behaves as cathode when coupled to alloys.The effects of chloride ion concentration, pH, temperature, nature of cations and anions, and resistance of the epoxy matrix to environmental agents on the rate of oxygen reduction reaction on GECM electrodes are reported. Moreover, polarization studies performed on GECM-aluminium alloy couples show that polarization occurs mainly at the composite interface.From potentiostatic anodic polarization curves of different alloys and cathodic polarization curves of GECM, the initial galvanic corrosion current densities for most alloy-GECM couples of interest in the aerospace industries have been obtained. These values are strongly affected by environment durability of the epoxy matrix and variation by one or two orders of magnitude are observed. Despite the latter discrepancy, these data can be helpful in the assesment of a galvanic series based on galvanic current density for alloy-GECM joints.     

Synthesis of carbon nanotubes by catalytic conversion of methane: Competition between active components of catalyst

Catalytic growth of carbon nanotubes from methane was studied as competitive catalytic process in situ of both oxidative (partial oxidation) and non-oxidative (pyrolysis) conversion. Ni and Fe may act as either competing or cooperative catalyst components in the process of carbon nanotubes growth. The competition between Ni and Fe in the process of carbon nanotube growth on Ni-Fe based stainless steel alloy during partial oxidation of methane results in suppression of Ni catalytic activity in favor of Fe. The discrimination is so strong that iron is segregated from Ni-Fe based stainless steel alloy leaving characteristic Ni-enriched corrosion caverns. Interaction between Ni and Fe during non-oxidative conversion, in contrast to the oxidative conversion, leads to cooperative effect; the activity of bimetallic catalyst increases as compared with monometallic one. Depending on particular catalyst bed composition, the nanotubes of various morphologies may occur. In particular, the use of perovskite-type catalyst for partial oxidation of methane leads to formation of “olive-branch”-like peculiar carbon nanostructures.     

TiCN and metallic coatings for corrosion protection of separator plates in MCFCs

Stainless steel 304 substrates were coated with different materials in order to find a suitable coating material for corrosion protection of separator plates in molten-carbonate fuel cells (MCFCs). Five titanium carbonitride coatings differing in composition and morphology and a titanium monoxide coating were deposited with chemical vapour deposition techniques. Also double-layer coatings of TiN/Au and TiN/Ni were prepared. The coatings were tested on their corrosion protection of separator plates in four different environments: under MCFC-cathode or anode gas, at load or at open circuit conditions. The corrosion behaviour was characterized using cyclic voltammetry. Corrosion rates were determined with electrochemical methods and cross-section analyses of corrosion layers. Titanium nitride coatings showed the best corrosion protection. The titanium carbide and titanium monoxide coating showed respectively less and no protection. The thin gold and Ni-coatings were unstable. Under cathode gas, the most important corrosion protection is given by keeping the cell at load, and then a titanium nitride coating might provide lifetime protection. Under anode gas, corrosion is most severe at load conditions. A titanium nitride coating also gives corrosion protection, but not enough for lifetime protection.     

碳钢沉积镍磷合金组合材料的力学与防护性能

对以４５＃钢为基体沉积镍磷合金层组合材料的力学性能、腐蚀磨损性能进行试验研究。与２Ｃｒ１３不锈钢相比,４５＃钢 镍磷合金组合材料力学性能相当,防护性能优良,能够代替２Ｃｒ１３不锈钢。     

Copper anode corrosion affects power generation in microbial fuel cells

Non‐corrosive, carbon‐based materials are usually used as anodes in microbial fuel cells (MFCs). In some cases, however, metals have been used that can corrode (e.g. copper) or that are corrosion resistant (e.g. stainless steel, SS). Corrosion could increase current through galvanic (abiotic) current production or by increasing exposed surface area, or decrease current due to generation of toxic products from corrosion. In order to directly examine the effects of using corrodible metal anodes, MFCs with Cu were compared with reactors using SS and carbon cloth anodes. MFCs with Cu anodes initially showed high current generation similar to abiotic controls, but subsequently they produced little power (2 mW m^‐2). Higher power was produced with microbes using SS (12 mW m^‐2) or carbon cloth (880 mW m^‐2) anodes, with no power generated by abiotic controls. These results demonstrate that copper is an unsuitable anode material, due to corrosion and likely copper toxicity to microorganisms. © 2013 Society of Chemical Industry     

PTA装置不锈钢材料腐蚀磨损的探讨

采用自制的实验装置,模拟PTA生产装置中回转式干燥机蒸汽列管工作条件,对奥氏体不锈钢0Cr18Ni9(304)、00Cr17Nd4Mo2(316 L)、00Cr19Ni13M03(317 L)和双相不锈钢00Cr22Ni5Mo3N(2205)在含有溴离子和对苯二甲酸颗粒的醋酸介质中,进行腐蚀磨损性能研究。结果表明,4种不锈钢的腐蚀磨损速率随着腐蚀介质温度的升高而增加;在低温时,腐蚀磨损速率差别不大;当温度超过80℃以后,腐蚀磨损性能的差异变大,其中2205的耐腐蚀磨损性能最好,其次为317 L,316 L,而304则最差。相同条件下,腐蚀磨损速率大于均匀腐蚀速率。建议用2205代替316 L制作PTA同转蒸汽管干燥机的加热列管。     

Cu/Ni复合仿生超滑表面耐蚀性能研究

本文针对碳钢在海洋环境中腐蚀严重的问题,采用水热法结合化学气相沉积技术及注入润滑油的三步法在碳钢表面制备了Cu/Ni复合仿生超滑表面。研究了仿生超滑表面对碳钢基体的腐蚀防护性能的影响。通过扫描电镜(SEM)、X射线光电子能谱(EDS)分析了碳钢表面水热反应2 h后形成的Cu/Ni涂层的形貌及组成成分;通过接触角测试分析了Cu/Ni疏水表面的润湿性;运用动电位极化曲线和交流阻抗谱(EIS)研究了仿生超滑表面在3.5 wt.%NaCl溶液中的耐蚀性能。结果表明,Cu/Ni膜层呈现微纳米级粗糙结构,Cu/Ni膜层疏水涂层与水滴的接触角为127.8±1°,Cu/Ni仿生超滑表面腐蚀电流密度为2.96×10-7A·cm-2,相比于碳钢基体降低了2个数量级,对碳钢基体具有一定腐蚀防护作用。     

Localized corrosion of carbon steel in a CO2-saturated oilfield formation water

In this work, corrosion and localized corrosion behavior of X65 pipeline steel were studied in a simulated, CO₂-saturated oilfield formation water by various electrochemical measurement techniques, including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves, galvanic current and localized EIS (LEIS). The morphology and composition of the formed corrosion scale were characterized by scanning electron microscopy and energy-dispersive X-ray analysis. A conceptual model was developed to illustrate the occurrence of localized corrosion of the steel under scale. Both galvanic current and LEIS measurements showed that a galvanic effect existed between the bare steel and the scale-covered region. The scale-covered region served as cathode and the bare steel site as the anode. The big cathode vs. small anode geometry accelerated the local corrosion reaction. At an elevated temperature, a compact, crystalline scale was formed on the steel surface, enhancing the galvanic effect. Moreover, the stability of the scale was increased with time, and localized corrosion of the steel under scale experienced mechanistic changes with time.     

Corrosion behaviour of NiTi alloy

In the present work, the corrosion behaviour of NiTi in Hanks’ solution at 37 °C was assessed by the use of electrochemical methods. Pure titanium and pure nickel were included in the study in order to understand the contribution of each alloying element. The results were compared with Ti-6Al-4V alloy and 316L stainless steel, materials traditionally used as orthopaedic implants. Moreover, the susceptibility of NiTi to corrosion under different conditions was examined using other physiological solutions and different pH values.It was observed that the corrosion behaviour of NiTi is much closer to Ti than to Ni, as it may be seen on the polarization curve, where the high protective character of the passive oxide film formed on NiTi is similar to that of titanium. On the other hand, comparing the different implant materials, it was possible to establish the following relation for their corrosion resistances: 316L stainless steel < NiTi < Ti-6Al-4V.     

A3碳钢在模拟油田水中的腐蚀行为研究

用极化曲线法探讨了A3碳钢在模拟油田水中的腐蚀电化学行为。试验了在不同矿化度、pH值、溶解氧及含S2-的模拟油田水中A3碳钢的腐蚀行为,并用电化学方法研究了缓蚀剂的缓蚀效果。结果表明,随着矿化度的增加,温度的升高,腐蚀速率增大;pH值在7~8之间为碳钢的钝化区;在中性或碱性条件下,碳钢的腐蚀主要受溶解氧的影响,溶解氧含量越高,腐蚀越严重;S2-的存在消除了溶解氧的影响,改变了腐蚀产物膜的组成,从而影响缓蚀剂的选择。     

Zn／A3钢在海水中电偶腐蚀的研究

研究了金属Zn与A3钢在海水中偶接时的电偶腐蚀行为。考察了偶接时间、溶液中Cr浓度、电偶对中阴阳极面积比、实验温度等因素对阳极腐蚀速度的影响。结果表明：偶接时间为24h时,腐蚀速度趋于稳定。腐蚀速度随温度升高,溶液中Cr浓度的增大;阴阳面积比的增大,A3钢的腐蚀速度会相应减慢。     

土酸介质中不锈钢高温缓蚀剂的评价

研制了一种土酸介质中不锈钢缓蚀剂,并采用了失重法、电化学方法和扫描电镜分析法对该缓蚀剂进行了评价。实验结果表明,该缓蚀剂具有优良的缓蚀性能、抗高温性能、抗干扰性能和抗非均匀腐蚀性能。该缓蚀剂安全使用浓度为0.5%,90℃时金属腐蚀速率仅为0.55 g/m2.h,20 h内随时间增长,金属腐蚀速率下降。该缓蚀剂属于混合型缓蚀剂,同时抑制阳极过程和阴极过程。在该缓蚀剂存在的土酸介质中,不锈钢不产生点蚀、晶间腐蚀等非均匀腐蚀现象。     

双相不锈钢管固液两相流动腐蚀的数值模拟

在碳钢流动腐蚀数值模拟的基础上,针对管道流动体系,对固液两相流条件下双相不锈钢的流动腐蚀进行了数值模拟.模拟了固液两相流体动力学过程和双相不锈钢腐蚀动力学过程,模拟计算得到的腐蚀速率与实测值基本一致,表明建立的两相不锈钢流动腐蚀的综合数学模型是正确的,揭示了两相流中双相不锈钢的流动腐蚀机理,并进行了实验验证.两相流中双相不锈钢流动腐蚀的加剧主要是由于颗粒相的存在会大大强化液相流体的流体力学因素,导致钝化膜内传质速度加快所致.计算结果同时也表明,对于表面覆盖有钝化膜的材料的数值模拟,建立合理的流动腐蚀动力学模型是数值计算方法应用成功与否的关键.