结合WBE与EIS技术研究环氧涂层下碳钢与铜合金在海水中的电偶腐蚀

目的 研究环氧涂层下碳钢与铜合金在海水中的电偶腐蚀行为及涂层整体和局部区域的劣化过程。方法 使用丝束电极（WBE）技术和电化学阻抗谱（EIS）技术研究丝束电极表面的电流密度分布和涂层阻抗谱演化,同时对比分析碳钢区域与铜合金区域涂层的阻抗谱特征。结果 阳极电流峰首先出现在碳钢局部区域,而电流密度较大的阴极电流峰主要集中出现在铜合金区域的边缘。当浸泡至122 h时,铜合金区域的涂层阻抗明显低于碳钢区域的涂层阻抗,且EIS响应出现了Warburg扩散阻抗特征。在浸泡456 h后,单根钢电极发生由阴极向阳极的极性转换。结论 涂层下碳钢与铜合金在海水中发生电偶腐蚀时,铜合金作为阴极被保护,但铜合金区域的涂层在阴极剥离的作用下加速劣化。在涂层劣化过程中,碳钢区域的涂层缺陷处成为腐蚀反应的阳极区,而主要的阴极区位于铜合金的边缘区域,这与溶解氧的“竞争效应”有关。由于涂层发生阴极剥离现象使得基底金属被腐蚀,从而导致涂层下单根钢电极的电流发生由阴极向阳极的极性转换。     

高氯介质中pH对316L不锈钢和Q235碳钢腐蚀行为的影响

采用电化学阻抗谱、极化曲线、丝束电极等技术研究了316L不锈钢和Q235碳钢在不同pH且含有高浓度氯化物的高炉煤气冷段管道冷凝液模拟液中的腐蚀行为。结果表明,随着溶液pH的升高,两种材料的阻抗值均逐渐增大,316L不锈钢的钝态电流密度和Q235碳钢的腐蚀电流密度均减小。丝束电极电流分布图中阳极电流区域随溶液pH的升高而减小,不锈钢和碳钢分别表现出局部腐蚀和全面腐蚀的特征。     

镧盐型缓蚀剂对Cu-Zn-Ni铜合金在3.5% NaCl溶液中的缓蚀作用

利用硝酸滴定试验、失重试验、动电位极化方法以及电化学阻抗谱技术,研究了Cu-Zn-Ni铜合金稀土镧盐型缓蚀剂,在3.5%NaCl溶液中的缓蚀作用。结果表明,协同型缓蚀剂BTA(苯并三氮唑)+TTA(甲基苯并三氮唑)和BTA+LaCl3能够很好地提高该铜合金在3.5%NaCl溶液中的耐腐蚀性能。当缓蚀剂中同时含有BTA、TTA、LaCl3(BTA:3g.L-1,TTA:14g.L-1,LaCl3:7g.L-1)时所表现出来的缓蚀效率最高。Cu-Zn-Ni合金经BTA+TTA+LaCl3缓蚀剂处理后,在NaCl溶液中室温下的腐蚀速率为2μm/a。     

碳钢在模拟一级反渗透产水和海水中的腐蚀行为比较

采用丝束电极测试(WBE)、电化学阻抗谱(EIS)和挂片失重法研究了静态条件下碳钢在模拟海水淡化一级反渗透(RO)产水和海水中的腐蚀形态及其电化学特性。结果表明,碳钢在模拟一级RO产水和海水中腐蚀电位随时间延长而下降;在模拟一级RO产水15d的试验中,碳钢表面微阴极、微阳极的最大电位差始终大于110mV,腐蚀过程中阴极、阳极区域位置基本不变,腐蚀始终在局部区域进行,阻抗谱显示一个时间常数;在模拟海水中2d后碳钢表面微阴极、微阳极的最大电位差小于10mV,微阴极、微阳极区域位置在不断变化,发生全面腐蚀,随着腐蚀的进行碳钢电极的电化学阻抗谱上出现Warburg阻抗,腐蚀过程逐渐发展为扩散控制,表面生成的致密腐蚀产物对碳钢的进一步腐蚀起到了一定的抑制作用,碳钢腐蚀速率下降。碳钢在模拟一级RO产水中的表观腐蚀速率略大于模拟海水,因其实际腐蚀部位面积小而局部区域的腐蚀速率比在海水中更大。     

ρ(Ca2+)对碳钢在NaHCO3- NaCI - CaCl2溶液中腐蚀行为的影响

利用计时电流和电化学阻抗测试技术,检测了碳钢在NaHCO3 - NaCl - CaCl2溶液中的腐蚀行为.通过分析计时电流法的平均腐蚀速率和试样表面相应的形貌分析以及分析电化学阻抗谱的电荷转移电阻,研究了不同的Ca2+的质量浓度对碳钢腐蚀行为的影响.结果表明:少量的Ca2+对碳钢的腐蚀有抑制作用,当溶液中的ρ(Ca2+)为640 mg/L时,极化曲线测得的平均腐蚀速率为3.253e - 4A/cm2,电化学阻抗测得的电荷转移电阻为29.480 kΩ.cm2,电极表面的损伤度为2.791,碳钢的腐蚀最轻微.     

ρ(Ca2+)对碳钢在NaHCO3- NaCI - CaCl2溶液中腐蚀行为的影响

利用计时电流和电化学阻抗测试技术,检测了碳钢在NaHCO3 - NaCl - CaCl2溶液中的腐蚀行为.通过分析计时电流法的平均腐蚀速率和试样表面相应的形貌分析以及分析电化学阻抗谱的电荷转移电阻,研究了不同的Ca2+的质量浓度对碳钢腐蚀行为的影响.结果表明:少量的Ca2+对碳钢的腐蚀有抑制作用,当溶液中的ρ(Ca2+...     

电化学交流阻抗法研究钨酸盐与BTA的协同缓蚀作用

通过电化学阻抗谱技术和表面分析方法研究了钨酸盐和苯并三氮唑对碳钢的协同缓蚀作用。结果发现 :在 pH =9.0 ,氯离子浓度为 5× 10 -3mol/L的水中 ,钨酸盐和BTA单独用作缓蚀剂对碳钢均有一定的缓蚀作用 ,钨酸盐和BTA具有协同缓蚀作用。提高溶液 pH、降低氯离子浓度有助于增强钨酸盐 BTA复配缓蚀作用。复配缓蚀剂的缓蚀机理为WO2 -4 与BTA分别与Fe3+ 和Fe2 + 发生反应生成稳定的膜覆盖于电极表面     

黄铜在含硫酸盐还原菌的模拟冷却水中的腐蚀行为

结合扫描电镜(SEM)及能谱(EDS)分析,采用电化学阻抗谱、极化曲线测试以及丝束电极(WBE)技术,对黄铜电极在含硫酸盐还原菌(SRB)的模拟冷却水中表面成膜及腐蚀状况进行了分析。结果表明,在含菌模拟冷却水溶液中,电极表面会形成一层生物膜,电极表面含有铜和硫等元素。电化学测试分析结果显示,随着浸泡时间延长,无菌溶液中铜电极的阻抗值不断增大,腐蚀电流密度下降;含菌溶液中铜电极的阻抗值则随时间减小,腐蚀电流密度显著增大;浸泡初期电极表面的极差较大,随时间延长极差不断减小,显示浸泡初期电极表面状态不一致性较大,可能是浸泡初期SRB在电极表面成膜不均匀,从而导致局部区域的腐蚀。     

Q235碳钢在静止和流动条件下的腐蚀不均匀性研究

目的研究Q235碳钢在静止和流动条件下腐蚀程度和主要腐蚀区域的差异。方法使用丝束电极(WBE)技术和电化学阻抗谱(EIS)技术分别研究了WBE在静止和流动条件下的电流密度分布、电荷转移电阻以及腐蚀形貌的变化和差异,同时分析了电极的极性转换现象。结果流动条件下Q235碳钢的电荷转移电阻明显降低。在静止条件下,Q235碳钢表面阳极电流区域所占的最大比例为47%,且阳极电流峰集中出现在WBE的中间区域,而四周边缘处的阳极电流峰较少。在流动条件下,Q235碳钢表面的阳极电流区域所占的最大比例为58%,阳极电流峰随机分布在整个WBE表面,且电流分布区间明显变窄。浸泡在静止条件下的58~#电极和流动条件下的39~#电极发生了多次极性转换现象。结论 Q235碳钢在静止和流动条件下均发生了明显的不均匀腐蚀现象。流动条件加剧了Q235碳钢的腐蚀且降低了腐蚀不均匀性。静止条件下Q235碳钢的腐蚀区域集中在中间区域,流动条件下Q235碳钢的腐蚀区域随机分布在整个碳钢表面。静止和流动条件下的钢电极均发生了电流的极性转换现象。     

碳钢电极在流动3.5%NaCl溶液中的电化学行为

用交流阻抗技术研究了普通碳钢电极在流动3.5%NaCl溶液中的阻抗谱特征.结果表明:无论是在流动的单相还是双相溶液中,碳钢电极的阻抗谱均为一单容抗半圆弧.随着流速增大,腐蚀反应阻抗(Rf)逐渐减小,腐蚀随之增大.当流速超过临界流速之后,其阻抗谱在低频区出现收缩现象.此时,不仅碳钢的均匀腐蚀越来越严重,而且其局部腐蚀也明显加剧.若对体系充氮除氧,则在相同流速下,其腐蚀反应阻抗显著增大,碳钢的腐蚀速率显著降低.     

Correlation between electrochemical impedance and current distribution of carbon steel under organic coating

The current distribution of carbon steel beneath intact organic coating exposed to 3.5% NaCl solution was investigated by the wire beam electrode (WBE) method. The electrochemical impedance spectroscopy (EIS) of individual electrodes with high current was characterized to analyze the behavior of the coating degradation and metal corrosion at coating/metal interface. The polarity switch of the electrode under the coating was observed. The mechanism of coating degradation and carbon steel substrate corrosion was discussed from a point of electrochemical distribution.     

Correlation of temperature with galvanic corrosion behaviour of copper alloys based on wire beam electrode

Galvanic corrosion behaviour of copper and copper alloys in chloride solution (0.6?M NaCl) under different temperature conditions (35°C, 55°C and 80°C) was investigated by the wire beam electrode (WBE) method. It was found that the average galvanic current of the Cu and Cu–Sn alloy, which shifted from the cathode at 35°C to the anode at 80°C, increased as temperature increased during the immersion time. In contrast, the average galvanic current of Cu–Zn alloy can be ranked as 35°C?>?55°C?>?80°C. A sudden conversion was that the anode average current of Cu–Zn alloy at 35, 55°C changed into the cathode when the immersion time lasted untill 3 h at 80°C. The results indicate that it is feasible to study the corrosion behaviour under the different temperature environment with the WBE method.     

WBE联合LP技术研究海水/海泥界面碳钢的腐蚀行为

利用阵列电极技术捕获了在不同浸泡时间下每个微电极与其它99个微电极整体的电偶电流,分析获得了海水/海泥界面附近阴、阳极分布区域的变化规律;利用线性极化和电化学阻抗技术对垂直海水/海泥界面的一行微电极进行测试,获得了距海水/海泥界面不同距离的微电极的腐蚀电流、腐蚀电位,并观察了腐蚀形貌,探讨了其腐蚀机理。结果表明：平行于海水/海泥界面的海泥区域为电偶腐蚀阳极区、对应的海水区域为电偶腐蚀阴极区域;海水/海泥界面区金属的腐蚀是由电位差、溶解氧浓度、海泥阻抗等多因素控制;腐蚀主要区域是近海水/海泥界面的海泥区域及远海水/海泥界面的海水区域。海水中较高浓度的氧促进了腐蚀产物的致密化,而海泥中缺氧环境及微生物抑制了腐蚀产物的致密化。     

Micro‐electrochemical characterization of galvanic corrosion of TA2/316L composite plate

Galvanic corrosion behavior of TA2/316L composite plate was investigated in the solution of 3.5 wt% NaCl by galvanic potential monitoring, scanning localized electrochemical impedance spectroscopy (LEIS) and scanning vibrating micro‐electrode (SVME) techniques. The results demonstrated that the pitting corrosion resistance of 316L for the galvanic combination sample is lower, and the coupled current density is higher than for the single 316L sample. It indicates that the galvanic action works on the corrosion behavior of the TA2 titanium alloy/316L stainless steel galvanic combination in sodium chloride solution. The galvanic effect width was determined as 1500 µm.     

Electrochemical evaluation of under-deposit corrosion and its inhibition using the wire beam electrode method

A new experimental method has been applied to evaluate under-deposit corrosion and its inhibition by means of an electrochemically integrated multi-electrode array, namely the wire beam electrode (WBE). Maps showing galvanic current and corrosion potential distributions were measured from a WBE surface that was partially covered by sand. Under-deposit corrosion did not occur during the exposure of the WBE to carbon dioxide saturated brine under ambient temperature. The introduction of corrosion inhibitor imidazoline and oxygen into the brine was found to significantly affect the patterns and rates of corrosion, leading to the initiation of under-deposit corrosion over the WBE.     

Corrosion protection of composite coating combining ceramic layer,copper layer and benzotriazole layer on magnesium alloy

A novel composite coating was fabricated on AZ91 magnesium alloy by applying a composite surface treatment which combined the methods of plasma electrolytic oxidation (PEO) pre-treatment, electroless copper and benzotriazole (BTA) passivation. The cross-section microstructures and chemical compositions of coating were examined using scanning electron microscopy (SEM) equipped with energy dispersive analysis of X-rays (EDX). Potentiodynamic polarization curves and salt spray tests were employed to evaluate corrosion protection of the coating to substrate in 5% NaCl solution. It is indicated that electroless copper produces a rough interface between the electroless copper layer and the ceramic layer. The corrosion potential shifts to the positive direction significantly and the current density decreases by more than one order of magnitude. There is no visible galvanic corrosion pits on the surface of the composite coating combination of PEO and electroless copper after 168 h neutral salt spray testing. The color of copper after BTA immersion could be held more than 60 d.     

NaNO2对20SiMn低合金钢在3％NaCl溶液中空蚀损伤的缓蚀作用

利用磁致伸缩空蚀实验机研究了20SiMn低合金钢在3%NaCl和3%NaCl＋NaNO2溶液中的空蚀行为.测量了静态和空蚀条件下的腐蚀电位变化、电化学阻抗谱和极化曲线.结果表明：NaNO2通过抑制腐蚀与空蚀间的交互作用，对20SiMn低合金钢在3%NaCl溶液中的空蚀损伤有良好的抑制作用，浓度为1%的NaNO2的缓蚀效率达到802%.添加NaNO2对20SiMn低合金钢在3%NaCl溶液中的电化学行为有显著影响.在3%NaCl溶液中，自腐蚀电位、线性极化电阻都随空蚀进行而逐渐负移和减小.与此相反，添加NaNO2后，20SiMn的自腐蚀电位、线性极化电阻都随空蚀的进行而逐渐正移和增大.3%NaCl+1%NaNO2溶液中的电化学阻抗谱特征与空蚀表面形貌的变化有较好的对应关系.     

NaCl液滴下304不锈钢表面电化学性质研究

利用丝束电极技术研究NaCl液滴下304不锈钢表面电化学参数分布及其随腐蚀时间的变化规律。结果表明,液滴下不锈钢丝束电极表面的腐蚀电位分布和电偶电流分布均呈现空间、时间上的不均匀性;丝束电极表面随机形成局部阴极区和阳极区,而且随着腐蚀时间的延长,局部区域的极性发生反转。液滴下电极表面的腐蚀程度和不均匀程度均随腐蚀时间的延长先增加后减小,在腐蚀12 h时达到最大。     

Heterogeneous corrosion of mild steel under SRB-biofilm characterised by electrochemical mapping technique

Heterogeneous corrosion of mild steel under sulphate reducing bacteria (SRB)-biofilm was characterised by wire beam electrode (WBE) technique and electrochemical impedance spectrum. The potential/current distributions of the WBE under SRB-biofilm showed that the potential maps could not indicate the localised corrosion of steels beneath biofilm due to the fact that all wire electrodes were short-circuited by the highly conductive sulphide precipitates embedded in SRB-biofilm. Instead, the galvanic current maps may give a good indication. The characteristic of super-capacitance (0.21 F/cm²) of SRB-biofilm was attributed to the huge specific surface area of conductive pore walls inside biofilm.