接地极Q235碳钢材料在上海土壤环境中的腐蚀行为

通过电化学阻抗 (EIS)、极化曲线、扫描电镜 (SEM)、能谱分析 (EDS) 和X射线衍射 (XRD) 等技术对接地极Q235碳钢材料在含不同盐分的上海地区土壤中的腐蚀行为进行了研究。结果表明,在不同盐分土壤条件下,Q235碳钢的阻抗均随着浸泡时间的延长出现先升高后平稳的趋势,腐蚀速率随盐分含量增大而增大。由于沿海土壤的侵蚀性阴离子含量较高,使得所产生的锈层失去保护性。Q235碳钢腐蚀主要以全面腐蚀为主,还伴有微生物腐蚀现象,腐蚀产物膜主要由Fe₂O₃组成。根据耐腐蚀性能评价标准,接地极碳钢材料在上海土壤环境中的耐腐蚀性能为良。     

耐蚀钢筋研究现状及腐蚀评价方法分析

在海洋环境中,钢筋锈蚀是导致混凝土失效的主要原因,提高钢筋耐蚀性是提高海洋环境中混凝土耐久性的根本。总结了近年来国内外耐蚀钢筋的种类及耐蚀钢筋的研究现状,并对混凝土中钢筋常用的物理检测方法和电化学检测方法进行了总结。评价了目前国内外常见的用于评价钢筋耐蚀性的方法的特点。     

渗锌钢在4种典型土壤环境中的腐蚀行为

在我国大港、鹰潭、格尔木、克拉玛依4个典型土壤中,将渗锌钢片埋藏2 a,观察试样的宏观形貌和微观形貌,用XRD物相结构检测分析了锈层的主要成分,计算渗锌钢在各试验站的腐蚀速率,并采用电化学测试分析了锈层对腐蚀介质的阻挡能力。结果表明,渗锌钢在4个土壤实验站的腐蚀速率均比较大,2 a后在鹰潭土壤中腐蚀速率最大,土壤的理化性能影响着渗锌钢腐蚀产物成分和相对含量。     

Regularities of the effect of cyclic polyether on the microstructure,kinetics of deposition,and some properties of nickel and organonickel coatings

Polarization studies showed that an increase in the crown ether content in a sulfate nickel-plating electrolyte results in a considerable increase in polarization of the cathodic process, a decrease in the current efficiency of metal and its deposition rate, and an improvement of the coating quality (adhesion, microhardness, uniformity, fineness of structure). Introduction of N-methylpyrrolidone (MP) into sulfate electrolyte decreases the efficiency of 15-crown-5: polarization curves are shifted into the region of less negative values, electrochemical control of the process is replaced by diffusion control. The appearance of the coating changes in the presence of ?-caprolactam (CL): it becomes more even and uniform, but contains microcracks indicating the presence of internal stresses in the deposit. The possibility of effective regulation of the deposition rate, microstructure, and properties of organonickel coatings through changing the bulk concentration of the crown ether, MP, and CL is shown.     

Stress Corrosion Test Methods

Abstract

In the hope that some of the pitfalls may in future be avoided, the paper discusses problems associated with the various methods of stress corrosion testing, without providing a catalogue of test methods. Thus, the use of time to failure as a parameter that measures susceptibility may lead to erroneous conclusions, whilst designers may be misled if they are not aware that K_ISCC values, as sometimes determined from pre-cracked specimen tests, are not as reproducible as those design parameters, such as yield stress or ultimate tensile stress, with which they are more familiar. The effects of specimen surface area, and its relation to solution volume, as well as surface finish, are among other quantities that may cause discrepancies between results from different laboratories. Similarly, in relation to environmental aspects of testing, the dangers in the use of ‘standard’ solutions are indicated and the necessity, in simulating service failures, of precisely reproducing the composition of the environment and the relevant electrode potential are shown, as well as the importance of other factors.     

盐渍土壤湿度变化对碳钢腐蚀的影响

利用电化学的研究方法对盐渍土壤湿度对碳钢腐蚀的影响进行了研究，由极化曲线拟合结果，对于盐湖盐渍土壤来说，最大腐蚀速度出现在20％左右的湿度。而在临界湿度左右时，腐蚀试样的阻抗弧最小，介质的阻抗最小。     

空调用电子膨胀阀应力腐蚀外漏原因分析

空调用电子膨胀阀在售后频繁出现外漏失效。采用扫描电镜、能谱分析、断口金相检验等分析方法,发现泄漏以阀体内侧为源,断面呈现沿晶脆性断裂及冰糖状腐蚀特征,析出大量氯化物,在阀体外表形成垂直于焊缝的多处近平行裂纹。金相组织评定显示晶间腐蚀倾向弱,为活化环境下的应力腐蚀失效。追溯制程发现清洗剂变质试验分解出Cl-,将电子膨胀阀浸入可再现售后失效。结合失效机理,制定辅料试验、残留标准,并进行外壳深冲、激光焊接约束拉应力控制,可有效防止故障发生。     

Hot Corrosion of Metals and Alloys

When metals and alloys are used at high temperatures, especially in combustion processes, deposits often accumulate on the metal surfaces and affect the oxidation processes. This paper is concerned with deposit-induced accelerated corrosion, or hot corrosion, of metals and alloys. Initially, the characteristics of hot corrosion are identified for Na₂SO₄ deposits in terms of the factors that influence the reaction process. It is shown that hot corrosion consists of initiation or incubation and propagation stages. During the initiation or incubation stage, the deposit is shown to not have a significant effect on the corrosion processes, but it is causing conditions to develop whereby the propagation stage characteristics are determined with attendant large increases in the corrosion rates. Type I, high temperature hot corrosion and Type II, low temperature hot corrosion are then described in terms of historical mechanistic perspectives. The dependence of Type I and Type II hot corrosion on temperature and SO₃ partial pressure is discussed along with future work that is needed in order to more completely understand these hot corrosion processes along with the effects of some elements such as Cr, Al, Mo, Co and Pt.     

Corrosion of uranium and its low content Zr, Nb, and Ru alloys in aqueous solutions

Corrosion of uranium and its alloys with low content (0.5–5.0 at %) of Zr, Nb, and Ru in water and bicarbonate aqueous solutions is studied; the effect of hydrogen peroxide, the main product of radiation processes, on the corrosion rate is elucidated. The rate of the primary corrosion process U +(2 +n)H₂O=UO₂·nH₂O+ 2H₂↑ is measured by electrochemical methods in anaerobic and aerobic conditions for uranium metal and its alloys containing 0.5 to 5.0 at % of Zr, Nb, and Ru. It is shown that the corrosion rates for the alloys are lower than that of reactor-grade uranium; however, the difference is rather close to the measurement error. The corrosion mechanism is studied; U(III) is shown to be rather unstable in neutral solutions when uranium(III) hydroxide is precipitated and no significant amount of U(III) and UH₃ is present among the products of the metallic uranium corrosion in water. The kinetics of the second corrosion stage U(IV) + O₂→U(VI) is studied by spectrophotometric method. It is shown that the reaction of U(IV) oxidation by atmospheric oxygen is similar in weakly acid solutions (pH 1.5–4.0) and in bicarbonate media: in particular, it has an induction period for uranium (IV) accumulation, after which the reaction accelerates; it is formally a first-order reaction with respect to uranium. The reaction mechanisms differ in the two media: in weakly acid solutions, after the appearance of U(VI), the reproportionation reaction proceeds; thus formed U(V) interacts with O₂ faster than U(IV). In the bicarbonate medium, the acceleration of the reaction is due to the formation of a [U(IV)ΣU(VI)] complex whose reactivity is higher than that of uranium (IV). In the absence of bicarbonate, of great importance is the formation of a copolymer of U(IV) and U(VI), which at pH≥4 prevents formation of U(V). It is shown that on the introduction of hydrogen peroxide to aqueous solutions, the metallic uranium surface becomes transpassive, which increases the rate of corrosion process by at least an order of magnitude,. The introducing of oxidants and platinum mesh lowers the hydrogen accumulation at 120–150°C and, hence, the hydrogen-explosion danger of the uranium-water-corrosion-products system. Methods of deposition of metal oxide (Tc, Ru, Mo, W) films onto uranium surfaces by immersing uranium metal into Tc(VII), Ru(VI), or Mo and W heteropoly compound solutions are studied. Original Russian Text ? V.F. Peretrukhin, A.G. Maslennikov, A.Yu. Tsivadze, C.H. Delegard, A.B. Yusov, V.P. Shilov, A.A. Bessonov, K.E. German, A.M. Fedoseev, L.P. Kazanskii, N.Yu. Budanova, A.V. Kareta, A.V. Gogolev, K.N. Gedgovd, G.S. Bulato, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 3, pp. 229–251.     

发动机缸套的空蚀磨损和腐蚀

对K38发动机缸套失效进行了研究，并探讨了缸套失效原因、失效形式以及失效过程中空蚀磨损和腐蚀的作用。结果表明，缸套表面以空蚀磨损破坏缸套中的石墨为主；缸套的次表层破坏是由于空蚀磨损和腐蚀交互作用，使缸套破坏速度加快；缸套深层局部破坏以沉积物腐蚀为主，空蚀磨损为沉积物腐蚀创造了条件。     

换热器腐蚀失效分析

在换热器定期检查的过程中,发现在换热器表面出现明显的缺口,从而导致换热器失效,为了研究换热器失效的原因,并防止此类事件再次发生,故采用金相分析、SEM和电化学方法对产生腐蚀穿孔的换热器E-715管板焊缝进行失效分析,研究了其腐蚀机理. 结果表明,换热器腐蚀穿孔是由于电化学腐蚀造成的,焊缝电极电位较低,母材电极电位较高,在服役介质中形成原电池,对焊缝造成腐蚀,并最终穿孔. 同时管程介质为烃类,碳含量较高,管体表面产生了渗碳.     

韧性体应力腐蚀机理模型

工业上常见的应力腐蚀(SCC)是一种具有低应力脆性解理特征的失效模式,同时SCC机理一直是近百年来的科学难点和研究热点。结合最新研究进展,综述了韧性体SCC机理模型。宏观上,SCC通常由敏感材料、特定环境和应力三因子构成,其失效准则遵循Griffith理论。微观上,重点分析了近几十年提出的SCC机理的构型、适用性和局限性。大体上,SCC微观机理主要包括滑移溶解模型、择优溶解模型、膜致解理模型、腐蚀促进塑性变形模型和环境断裂一致性模型。尽管各模型对SCC的物理化学本质尚存争议,但从阳极溶解到膜破裂、位错滑移到脆性解理、氢的促进作用到电负性粒子的耦合作用,各模型对SCC的认识已逐步深化,已深入至原子尺度,具有重要理论意义和应用价值。此外,还展望了SCC前沿科学与应用前景。     

Derivation,Parameterization and Validation of a Sandy-Clay Material Model for Use in Landmine Detonation Computational Analyses

A set of large-strain/high-deformation-rate/high-pressure material models for sand-based soils with different saturation levels and clay and gravel contents was recently proposed and validated in our study, and the same has been extended in this study to include clay-based soils of different saturation levels and sand contents. The model includes an equation of state which reveals the material response under hydrostatic pressure, a strength model which captures material elastic-plastic response under shear, and a failure model which defines the laws and conditions for the initiation and evolution of damage and ultimate failure of the material under negative pressure and/or shear. The model was first parameterized using various open-literature experimental results and property correlation analyses and, then, validated by comparing the computational results obtained in an ANSYS/Autodyn-based transient non-linear dynamics analysis of detonation of a landmine buried in sandy-clay with their experimental counterparts.     

油气管道腐蚀与防护研究进展

随着管网的复杂化和管道腐蚀的多样化,管道老化问题日益显著,管道失效事故发生率上升,造成巨大的经济损失。分析了油管腐蚀的影响因素,管外土壤、管内输送介质及管杆腐蚀磨损是引起油管腐蚀的重要因素。归纳了油管腐蚀的一般特征,油管腐蚀是多种介质综合作用的结果,系统性总结了H_2S、CO_2腐蚀机理。H_2S腐蚀速率与其浓度呈正比关系,在浓度一定时,H_2S腐蚀速率主要取决于材料的硬度和强度。CO2腐蚀速率主要受温度、压力、介质流速以及pH值的影响。通过比较分析多种油管防护方法的优缺点,指出爆炸复合油管防护性能强且有效期长,是一种最适合油气井长效防护的方法。对管道施加外防护层和内壁检测是油管防护的有效手段,有益于降低油管事故率和提高油田综合效益。     

废气再循环单向阀阀片失效分析及腐蚀防护

目的 明确废气再循环(Exhaust Gas Recirculation,EGR)单向阀阀片的腐蚀失效机理及防护涂层的失效过程,提高其服役寿命和可靠性。方法 利用电火花直读光谱仪、金相显微镜、体视显微镜、扫描电子显微镜和能谱仪等对EGR单向阀阀片断裂件进行失效分析,表征其化学成分、宏观腐蚀形貌、微观腐蚀形貌及腐蚀产物的元素分布,明确失效机制。采用电化学测试方法和浸泡试验对比研究了3种涂层防护的有效性,包括聚四氟乙烯(Polytetrafluoroethylene,PTFE)、淬火–抛光–淬火(Quench-Polish-Quench,QPQ)+PTFE和聚酰胺酰亚胺涂层,揭示EGR单向阀阀片的腐蚀失效机理及防护涂层的失效过程。结果 EGR单向阀阀片表面及断口腐蚀严重。随着浸泡时间的延长,3种涂层的吸水率增加。涂层电容增大而电荷转移电阻减小,涂层的防护性能降低。30 d的浸泡试验结果显示,聚酰胺酰亚胺涂层的耐蚀性最好,涂层剥落少,其次是PTFE涂层,而QPQ+PTFE涂层的耐蚀性最差,涂层大面积脱落且划痕处和阀片边缘出现了明显的腐蚀产物。结论 EGR单向阀阀片断裂的主要原因是腐蚀降低了单向阀阀片的承载能力,在应力作用下发生断裂而失效;受涂层厚度限制,3种涂层在浸泡24 h后均发生溶液渗入涂层到达涂层/金属基体界面的过程,涂层的耐渗水性能低。聚酰胺酰亚胺涂层和PTFE涂层可以作为防护涂层,能在一定程度上提高单向阀的服役寿命。     

AgCu28合金的织构组织与力学性能

用X射线衍射法研究AgCu28合金的轧制变形织构组织和退火织构组织,对它们的延伸率和抗拉强度进行测试。结果表明,当AgCu28合金轧制变形量为95%时,Ag和Cu的主要变形织构是{110}112Brass织构;在H2气氛下经650℃,1.5h退火后,AgCu28的退火织构与变形织构相同;加工态AgCu28合金沿横向(TD)和轧制方向(RD)的抗拉强度分别为750和680MPa,退火态AgCu28合金沿TD和RD的抗拉强度分别是374和327MPa;退火态沿TD和RD的延伸率都约为12%。这表明在两元共晶合金中两相晶粒相互影响导致它们的变形织构与退火织构一致、晶粒显著细化、再结晶温度明显提高、抗拉强度显著提高并存在各向异性。     

微生物对Q235钢在黄壤土中腐蚀行为的影响

利用电化学阻抗(EIS)、极化曲线、扫描电镜(SEM)和表面能谱(EDS)等测试方法,研究了微生物对Q235钢在黄壤土中腐蚀行为的影响.结果表明:微生物加速了Q235钢在黄壤土中的腐蚀;试样在接菌和灭菌黄壤土中的电化学阻抗谱均为单容抗孤,在接菌土壤中发生了阴极去极化,其腐蚀速率高于在灭菌土壤中的腐蚀速率;随着腐蚀的进行...     

高温高压气井管柱腐蚀现状及未来研究展望

高温、高压、高腐蚀性介质引起的管柱腐蚀问题已成为国内外高温高压气井井筒完整性的巨大威胁和挑战。首先分析了我国塔里木盆地高温高压气井管柱服役工况环境、作业生产工艺、管柱受力情况以及腐蚀现状,重点回顾了国内外高温高压气井增产改造阶段酸化液引起的腐蚀、氯离子/硫化氢/环空保护液引起的应力腐蚀开裂、管柱接头缝隙腐蚀3种主要的失效形式,同时结合文献研究和现场失效案例分析总结了管柱腐蚀机理和规律。最后总结了高温高压气井管柱未来5大研究方向:基于生命全周期选材评价、15Cr和17Cr新管材、特殊管材酸化缓蚀剂、环空保护液应力腐蚀开裂敏感性、全尺寸管柱腐蚀实验方法。     

腐蚀和残余应力对油气管道不规则区可靠性的影响分析

目的针对油气管道的运行安全问题,建立油气管道局部腐蚀模型,对管道不规则区域的可靠性进行准确分析。方法首先,对管网中不同的不规则区域管道的腐蚀进行简单分析,每个区域都有局部腐蚀缺陷,任何区域的破坏都会导致整个管网的破坏。其次,定义各区域的有限元模型,考虑文献中给出的局部腐蚀模型和常用应力模型。再次,利用概率分析方法给出真实的腐蚀参数和时间模型,并采用蒙特卡洛模拟算法进行求解,得出不同腐蚀速率下管道的不规则区域的失效概率。最后,以三种不同腐蚀速率的数值算例分析各种因素对腐蚀管道可靠性的影响。结果受腐蚀和残余应力的影响,不规则区域的可靠性明显大于规则区域。考虑不同区域的残余应力,破坏概率随残余应力的增加而增加,特别是高腐蚀速率时,失效概率增加,而低腐蚀速率时,这种敏感性降低。法兰的可靠性更受有无残余应力腐蚀的影响。常规区(基)的可靠性最好。结论管道不规则区域对腐蚀和残余应力的响应机制不同于规则区域,所提出的方法相比于传统方法,能够更有效地评价不规则区域的可靠性。     

硫磺再生塔内件腐蚀失效分析

目的查明硫磺再生塔内件腐蚀失效的原因,提出避免该内件再次失效的对策。方法采用目测、金相显微镜和电子显微镜以及能谱分析等手段,分析内件腐蚀失效的原因。结果能谱分析表明,该内件基体镍含量偏低,腐蚀产物中硫含量较高。目测可见内件断口表面粗糙,电子显微镜形貌与金相显微分析表明,在晶界处有大量颗粒状碳化物析出。结论导致该内件失效的原因主要是热处理不当,造成了晶间碳化物的析出,从而导致了晶间腐蚀的发生。同时镍含量偏低也降低了材料的耐蚀性,含硫腐蚀性介质的冲刷作用也加重了低耐蚀性内件的晶间腐蚀。应使用化学成分符合国标304不锈钢材料生产的内件,同时要避免内件在生产与使用过程中因热处理不当造成晶间碳化物的析出。