干/湿NaCl盐雾条件下钢芯铝绞(ACSR)导线腐蚀层结构及腐蚀机理

采用干/湿NaCl盐雾试验,研究了钢芯铝绞(ACSR)导线腐蚀产物的相组成、腐蚀层结构及其腐蚀机理。结果表明:ACSR导线的腐蚀是氧化膜的局部破坏(形成麻点和缺口)及线股间电化学腐蚀等共同作用的结果。ACSR导线腐蚀产物组成复杂,主要包括锌及铝的氢氧化物及碱式氯化物盐。内外层Al股线及钢芯线表面镀锌层开始生成局部的麻点,然后形成连续的腐蚀层,腐蚀层内层致密而外层疏松。在腐蚀前期(≤168 h),外层铝股线的腐蚀速率大于内层铝股线,在腐蚀后期,内层铝股线的腐蚀速率更大。镀锌层的腐蚀速率最大,480 h腐蚀后完全被破坏,逐渐失去对钢芯线的保护作用。     

X70管线钢埋弧自动焊接接头的盐雾腐蚀行为

利用扫描电镜对X70管线钢焊接接头微观结构进行了观察,采用中性5%连续盐雾试验考察了其焊接接头表面的腐蚀性能,分析了X70管线钢焊接接头在盐雾介质中腐蚀行为,对点蚀坑内腐蚀产物进行EDS分析,探讨了X70管线钢焊接接头表面点蚀机理。结果表明,X70管线钢焊接接头在盐雾环境中耐蚀性低,容易诱发局部点蚀,Cl-对X70管线钢焊接接头的腐蚀起主导作用;其腐蚀过程主要由表面点蚀、形成腐蚀产物层、裸露的焊接接头表面腐蚀等3个部分组成,其中点蚀是裂纹萌生和扩展的主要来源;腐蚀产物主要是由Fe的氧化物和少量Fe的氯化物构成,其形成的氧化膜提高了其防盐雾腐蚀能力。     

在役输电线路钢芯铝绞线腐蚀状态评估与分析

为研究在役钢芯铝绞线(ACSR)的腐蚀状态,对典型气候下其各组成部分的腐蚀情况进行了宏观和微观研究,并结合其运行环境,分析了腐蚀原因。结果表明,腐蚀较为严重的是外层铝绞线,局部已出现腐蚀坑,钢芯基体未发生明显腐蚀;腐蚀产物可以降低铝绞线的腐蚀速率,但其对钢芯的腐蚀速率有提高作用。建议应更加注重外层铝绞线的腐蚀监测工作。     

35kV架空输电线路钢芯铝绞线内层铝股线的腐蚀失效分析

采用SEM和EDS对福建省某海岛上失效的35kV钢芯铝绞线进行表面和断口的形貌观察和成分分析。结果表明,表面主要由铝,Al(OH)3和Al5(CO3)3(OH)13·xH2O等物相组成,组成的元素除了铝、氧外,还含有碳、硅、硫、氯、钠、镁、钙等。碳、硅等元素集中在表面以及距表面250~500μm处。海洋大气、CO2和尘埃等腐蚀介质导致内层铝股线严重腐蚀,大量腐蚀产物粘附在基体上,表面上有以腐蚀区域为核心的发散裂纹。在腐蚀、振动和线张力的作用下,疲劳裂纹扩展带呈现半椭圆轮廓线,最终导致材料断裂。     

铝青铜在不同流速海水泥浆下的冲刷腐蚀行为

通过扫描电镜、电化学阻抗谱和电化学噪声和腐蚀测试,研究了铝青铜在静态海水、2 m/s和4 m/s海水泥浆下的冲刷腐蚀行为。结果表明：在静态海水中,腐蚀前期铝青铜表面以点蚀为主,腐蚀后期铝青铜表面腐蚀产物的积累使腐蚀性粒子传输困难,电化学腐蚀速率逐渐降低;在2 m/s海水冲刷下,铝青铜表面点蚀较严重,腐蚀主要受扩散控制,腐蚀产物的脱落使其腐蚀速率增大;在4 m/s海水冲刷下,腐蚀初期铝青铜表面以点蚀为主,受扩散影响,腐蚀后期,成核生长能量上升,铝青铜的腐蚀速率先降低后保持稳定。     

架空导线不同防腐措施的耐腐蚀性能比较

为探究常见架空导线耐腐蚀性能,对普通钢芯铝绞线、铝包钢芯铝绞线、防腐型钢芯铝绞线和碳纤维复合材料芯架空导线进行中性盐雾腐蚀实验。结果表明：普通钢芯铝绞线的腐蚀情况最为严重;而铝包钢芯铝绞线因避免了异种金属接触,内层铝线和铝包钢线表面腐蚀程度较低,表明铝包钢芯铝绞线耐蚀性优于普通钢芯铝绞线。防腐型钢芯铝绞线由于防腐脂的物理隔绝作用,受到防腐脂保护的铝线和钢芯在实验周期内均未见明显腐蚀迹象。而碳纤维复合材料芯导线,因碳纤维复合材料芯化学性质稳定,耐腐蚀性能优异,其紧密绞合的型线阻止了腐蚀介质向绞线内部渗透,绞线的耐腐蚀性能显著优于普通导线。     

福建某海岛架空输电钢芯铝绞线的失效分析

采用XRD、SEM和EDS对福建省某海岛上35 k V失效的钢芯铝绞线进行形貌和成分分析。结果表明:内层铝绞线表面主要由Al、Al(OH)3和Al5(CO3)3(OH)13·x H2O等物相组成。在断口上除了Al、O等元素外,还含有C、S、Cl、Na、Mg、Ca等。海洋大气、CO2和尘埃等腐蚀介质导致内层铝股线遭受潮的海洋大气腐蚀、应力腐蚀、小孔腐蚀等,使内层铝股线严重腐蚀。     

模拟酸雨溶液中应力对镀锌钢绞线腐蚀行为影响

通过Tafel直线外推法研究不同应力作用下斜拉桥拉索镀锌钢绞线在模拟酸雨溶液中的腐蚀行为,采用SEM、XRD、DTA-TG表征钢绞线镀锌层腐蚀后表面形貌、腐蚀产物理化性质.结果表明,随着应力增加,镀锌钢绞线极化电阻变小,腐蚀电流密度增大,且在1120MPa应力作用下镀锌钢绞线腐蚀电流密度达最大值,为无应力作用下腐蚀电流密度的7倍; 镀锌层发生局部电化学腐蚀,腐蚀后表面出现少量蚀坑,腐蚀产物填满这些蚀坑,覆盖于镀锌层表面,生成的白色腐蚀产物主要是ZnSO4•H2O.     

NY-400 型耐张线夹内部交流腐蚀形貌及产物研究

目的研究老旧高压输电耐张线夹内部交流腐蚀。方法截取已运行35 a的耐张线夹并解剖,采用扫描电子显微镜分析腐蚀区的微观形貌,采用X射线衍射仪、能谱仪和X射线光电子能谱仪对腐蚀区元素及物相进行分析鉴定,分析线夹内部腐蚀损伤演化过程。结果线夹内表面与铝线表面局部出现大量白色腐蚀产物和黑色覆盖物,白色腐蚀物呈粉末和片层两种形态。分析表明,腐蚀产物相组成为Al2O3,Al O(OH)和Al OOH;黑色覆盖物随深度增加而减少,黑色区域主要元素为Al,O和C,物相组成为Al2O3,C(graphite)和含C有机物。钢芯锌层破坏区的内层铝线更易腐蚀,腐蚀区呈灰黑色,微观形貌为富铁元素颗粒镶嵌在其它腐蚀产物中,区域的主要元素为Al,C,O,Fe和Zn,Fe元素存在形式为Fe2O3;钢芯表面镀锌层局部腐蚀严重,呈现平面型点蚀形貌,主要元素为Zn,Al,C和O,Zn腐蚀产物为六边纤锌矿结构Zn O。结论内部交流腐蚀原因为液体渗入,同时腐蚀产生大量的热致使材料分解。     

3Cr管线钢CO_2腐蚀实验研究

用线性极化法(LPR)研究了3Cr管线钢在高温高压CO_2腐蚀环境下的腐蚀速率,利用电化学阻抗谱(EIS)结合SEM与EDS研究了腐蚀不同时间的腐蚀产物膜.利用EIS监测到腐蚀产物膜中出现二次富Cr程度低的内层膜,并对其进行了分析.结果表明,腐蚀产物膜分为向基体内部原位生长的非晶富Cr层与腐蚀后期在其上沉积的FeCO_3晶粒层两部分,腐蚀膜内含Cr化合物的不断富集和致密度的提高,是腐蚀速率持续下降的主因;含Cr化合物的成膜需要一定的Cr~(3+)浓度;由于3Cr管线钢的点蚀源处的局部腐蚀速率较快,导致Cr~(3+)局部富集成膜,使点蚀源内腐蚀产物膜Cr/Fe比远高于周围,从而抑制了蚀坑的发展.     

Electrochemical noise monitoring of the atmospheric corrosion of steels: identifying corrosion form using wavelet analysis

The early stage atmospheric corrosion of T91 and Q235B steels exposed to Tianjin’s urban atmosphere over 20 days was studied using two electrochemical probes via an electrochemical noise (EN) technique. To identify the corrosion process and the corrosion form of the two steels, EN data were analysed by statistics and wavelet transform. The results revealed that the wavelet energy of decomposed EN mainly located at high-frequency level for Q235B steel, whereas it mainly located at the low-frequency level for T91 steel. Analyses of surface images confirmed that Q235B steel underwent uniform corrosion whereas T91 steel suffered from localised corrosion. The obtained noise resistance correlated well with weight loss data.     

Influence of electric current on the corrosion behavior of Cu for the electric contact in the isolation switch

The flow of electric current through the conductor has a far‐reaching effect on its corrosion behavior. In this paper, the effect of current on the corrosion behavior of Cu is investigated. The accelerated corrosion test of Cu with various external currents from 1 A to 5 A are carried out in 5% NaCl neutral salt spray environment. The results show that the samples with external current exhibit a faster corrosion rate than those without current. The corrosion kinetics and underlying mechanism are also discussed in this paper.     

Studies on waterline corrosion processes and corrosion product characteristics of carbon steel in 3.5 wt% NaCl solution

The waterline corrosion behaviors of carbon steel partially immersed in a 3.5 wt% NaCl solution were investigated using the wire beam electrode technique, and the effects of corrosion products on the processes of waterline corrosion were analyzed. The results demonstrated that the initial stage and development stage of waterline corrosion were mainly controlled by the concentration and diffusion of dissolved oxygen, respectively, and the deceleration stage of waterline corrosion was mainly affected by corrosion products. The main component of the yellow corrosion products was γ-FeOOH, and γ-FeOOH that exhibited a high reduction reactivity could be involved in the cathodic reaction. The black corrosion products were mainly composed of Fe₃O₄ with strong thermodynamic stability and the processes of dissolved oxygen diffusion and ion transports were obviously affected due to the continuous accumulation of Fe₃O₄ on the surface of the electrodes. Polarity reversals were observed on the single electrodes below the waterline, but the reasons for the phenomena were different from each other.     

Effects of alternating magnetic field on the corrosion rate and corrosion products of copper

The effects of alternating magnetic field on the corrosion morphologies, corrosion rate, and corrosion products of copper in 3.5% NaCl solution, sea water, and magnetized sea water were investigated using electrochemical test, scanning electron microscopy/energy dispersive analysis system of X-ray (SEM/EDAX), and X-ray diffraction (XRD). The results show that the corrosion rate of copper in magnetized sea water is minimal. Moreover, the surface of the specimen in magnetized sea water is uniform and compact as compared with those in 3.5% NaCl solution and sea water. The corrosion products of copper in magnetized sea water are mainly Cu2O and CuCl2. However, the corrosion products in sea water are CuCl, Cu2Cl(OH)3, and FeCl3·6H2O. The electrochemical corrosion mechanisms of copper in the three media were also discussed.     

The study on corrosion resistance of high-strength spring steel

The corrosion resistance in medium carbon high-strength spring steel was investigated in neutral salt spray of 5% NaCl solution and potentiodynamic polarisation measurements. The results showed that the corrosion process in the salt spray environment could be divided into two stages. In the initial corrosion stage, the corrosion rates of tested steels were high and rapidly decreased with increasing corrosion time. At later stages where rust layers formed and the corrosion rates of the tested steels all tended to be stable, corrosion resistance was reinforced with the increase of alloying elements, which is just new finding about formation and evolution of corrosion products of spring steel to improve corrosion resistance further in this research. The observation of corrosion products of the tested steels by energy dispersive spectroscopy and electron probe micro-analysis indicated that both Cr and V which had an obvious synergy concentrated mainly in the inner region of the rust layers, and the corrosion medium Cl^– was mainly distributed in the outer region of the rust layers.     

冶金因素对低合金钢焊接接头耐蚀性的影响

选择四种低合金钢并采用相应配套焊接材料,制备了焊条电弧焊焊接接头试样,通过室内腐蚀挂片试验和电化学测试,研究了焊接接头的不同区域的腐蚀行为,结合化学成分、夹杂物和微观组织分析,探讨相关冶金因素对接头腐蚀行为的影响.结果表明,对于不同钢的焊接接头而言,各接头母材之间、热影响区之间的腐蚀差异主要与其化学成分有关,但焊缝金属和熔合区之间的腐蚀差异则主要取决于夹杂物和微观组织.而同一焊接接头的不同区域的耐蚀性表现了较大差别,有的以焊缝的耐蚀性较差,有的则以母材的耐蚀性较差,导致不同区域耐蚀性差异的主要因素是化学成分、夹杂物、微观组织等.

Abstract：

The corrosion behaviors of four low-alloy steels welded joints have been studied by indoor exposure tests and electrochemical tests and the composition, inclusions and microstructures of such joints were also researched, For the different joints, the corrosion resistance of the parent-metal and heat-affect-zone is mainly dependent on the compositions of the steels; while the corrosion resistance of the welded bonds and welded metal is mainly dependent on inclusions and microstrures. For three distinct zones of the same welded joint, the corrosion resistance is different from each other. The corrosion resistance of distinct zones for the same welded joint is closely related to the chemical compositions, inclusions and micro-structures of the distinct zones respectively.     

Remote detection of corrosion activity by SQUID magnetometry across a multiphase medium under electrolyte flow conditions

Hydrodynamic induction of magnetic fields on AA2024 sample corroding in NaOH solutions was studied by a Superconducting Quantum Interference Device (SQUID) magnetometer operating in liquid helium with a spatial resolution of approximately 1 mm. The hydrodynamic generation of magnetic fields was explained in terms of electronic and ionic currents induced by corrosion potential gradients within the sample due to different solution flow velocities. The intrinsic magnetic activity of the electrolyte flow was significantly less than that of the corroding sample. The measurements demonstrated a unique capability of magnetometry to sense corrosion remotely and across the integrated media consisting of gaseous and solid dielectrics (air, plastics), electronic conductor (aluminum alloy) and ionic one (solution).     

Hot corrosion of materials: a fluxing mechanism?

Hot corrosion is the accelerated oxidation of a material at elevated temperature induced by a thin film of fused salt deposit. Fused Na₂SO₄, which is the dominant salt involved in hot corrosion, is an ionic conductor, so that the corrosion mechanism is certainly electrochemical in nature. Further, the acid/base nature of this oxyanion salt offers the possibility for the dissolution (fluxing) of the normally protective oxide scale. Non-protective precipitated oxide particles are often observed in the corrosion products. In this paper, the status of knowledge for the solubilities of oxides in fused Na₂SO₄ is reviewed, and the effects of various influences on a fluxing mechanism are discussed. An evaluation of a “negative solubility gradient” as a criterion for continuing hot corrosion is made.     

FeCo基大块非晶合金盐雾与电化学腐蚀研究

通过电化学测试方法与中性盐雾腐蚀实验研究Fe24 xCo24-xCr15Mo14C15B6Y2 (X=0, 2, 4, 6, 17)块体非晶合金的耐蚀性。合金在1 mol/L HCl中出现了宽的钝化区,其EIS图谱均由单一容抗弧组成,显示出良好耐蚀性;结合极化曲线与交流阻抗结果分析可得合金耐蚀性随着Co含量的增加先增大后减小,当Co含量为20%时合金耐蚀性最好。利用能谱分析(EDS)与原子力显微镜(AFM)对合金的中性盐雾腐蚀结果进行分析,可知它们的腐蚀产物主要由铁和钴的氧化物以及它们的氯化物组成。同时FeCo基大块非晶合金腐蚀程度随着Co含量的变化而变化,其盐雾腐蚀耐蚀性规律与电化学腐蚀耐蚀性规律一致。