腐蚀金属电极的电化学频域测量研究进展──金属腐蚀与防护研究所电化学研究介绍之一

腐蚀金属电极的电化学频域测量研究进展──金属腐蚀与防护研究所电化学研究介绍之一曹楚南（金属腐蚀与防护国家重点实验室,金属腐蚀与防护研究所,沈阳１１００１５）腐蚀电化学是研究与腐蚀有关的电化学问题,具体的研究对象为腐蚀金属电极。虽然电化学中的基本原理和...     

Online Monitoring of the Atmospheric Corrosion of Aluminium Alloys Using Electrochemical Noise Technique

In this work, an electrochemical system based on electrochemical noise (EN) technique for online detection and monitoring of atmospheric corrosion of LY12CZ aluminium alloys has been established. A detecting probe and a monitoring instrument with a software have been developed to perform the electrochemical noise measurements with zero resistance ammeter (ZRA) mode. Experimental results show that the atmospheric corrosion behaviour of aluminium could be effectively detected and monitored by the analysis of the electrochemical potential and current noise, also by the noise resistance variation.     

Surface analytical investigation of the electrochemical and corrosion behaviour of nanocrystalline FeAl8

From the higher fraction of grain boundaries in nanocrystalline substances a different corrosion behaviour in comparison to the conventional polycrystalline material can be expected, which may be utilised for the development of new corrosion resistant alloys. Therefore, the oxidation behaviour of these two different crystallisation states of FeAl8 was compared by means of electrochemical and surface analytical experiments. The oxide films formed after electrochemical passivation were investigated by Auger Electron Spectroscopy. The application of inelastic peak shape analysis by the method of Tougaard showed, that for both materials the oxide layer may be described by a model of a (below the contamination) buried layer with a thickness of only a few nanometers depending on the preparation conditions. Factor Analysis was applied for the evaluation of the differentiated low energy Auger electron spectra (20–100 eV) as a function of depth profiling sputtering time. For both, the nanocrystalline and the polycrystalline material, the inner part of the oxide layer was enriched in Al, whereas the very outer part (surface region) was enriched in Fe. No differences concerning the sputtering time for removal of the oxide layers were found for the two alloys.     

Corrosion monitoring using electrochemical noise and linear polarization resistance in fuel oil combustion gas environment

Corrosion monitoring of different steels is carried out online in a combustion rig firing 32 kg/h of fuel oil. Two temperature-controlled probes are designed to allow control of the specimens temperature and the use of electrochemical noise (EN) and linear polarization resistance (LPR) techniques for corrosion monitoring. Two probes are placed where the combustion gas reached a temperature of 850–900°C, and another one at the combustion gas exit where the rig was at 200–240°C. Corrosion rates of an austenitic and a ferritic steel are obtained where the temperature of the combustion gas is 850–900°C, firing fuel oils with different content of Na-V-S. Corrosion monitoring of mild steel is carried out in the test burning a fuel oil with the higher content of Na-V-S by placing a corrosion probe in the low combustion gas temperature zone. The EN results show that this technique is able to assess the corrosion rate in an environment at high temperature where fuel oil ashes deposited and at a temperature high enough where they start to melt and a corrosion process proceeds. Results show that this technique is able to assess the corrosivity of fuel oil ashes originated from fuel oil containing different amounts of sodium, vanadium, and sulfur as corrosion causing impurities. Results of the low-temperature probe show that EN and LPR are able to detect the onset of corrosion on mild steel as a result of sulfuric acid condensation on the probe. However, the corrosion rates are not the same, because localized corrosion is taking place as detected by the EN technique. It is demonstrated that the use of two techniques for corrosion monitoring can give a better understanding of the corrosion process. Electrochemical techniques used to assess the corrosion resistance of alloys at high and low temperatures prove to be a valuable tool for the purposes of materials selection or controlling the main process variables that affect the corrosion resistance of materials in industrial equipment. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 5, pp. 627–632. The text was submitted by the authors in English.     

Q235碳钢缝隙腐蚀的电化学噪声研究

应用电化学噪声和电化学阻抗技术研究Q235碳钢在NaHCO3+NaCl溶液中的缝隙腐蚀行为.结果显示,缝隙腐蚀过程可以被清楚地划分为3个阶段:孕育期、快速转换期和稳定发展期.电化学噪声的特征和噪声电阻在各阶段有着显著的变化.缝隙外、内表面积比(r)对缝隙腐蚀的孕育和发展有着十分重要的影响:r越大,孕育期越长.但是,在缝隙腐蚀稳定发展期,r较小时,缝隙外电极表面处于活性溶解状态,缝隙内外电位差很小,缝隙内腐蚀速率较小;倘如r很大时,则缝隙外电极表面处于钝态,缝隙内外电位差大,最终将导致严重的缝隙腐蚀.     

Detection of SCC of 304 NG stainless steel in an acidic NaCl solution using electrochemical noise based on chaos and wavelet analysis

The stress corrosion crack (SCC) of 304 nuclear grade (NG) stainless steel (SS) in 0.5 mol/L NaCl+1.5 mol/L H₂SO₄ was monitored using electrochemical noise (EN) based on chaos theory, statistics and wavelet analysis. The results indicated that the SCC process was divided into three stages according to the transient features in the EN. In the beginning, compared with the sample without applied stress, the enhanced fluctuation amplitude in the electrochemical current noise (ECN) of the stressed samples was attributed to stress-enhanced pitting corrosion and uniform corrosion; then the fluctuations of ECN for all the samples decreased due to a coverage by the corrosion products; however, the ECN fluctuations of stressed sample were larger than the unstressed sample, suggesting that the stress enhanced the SCC initiation and propagation. Chaos analysis revealed that the correlation dimensions increase from 2.1 to 2.5 during the corrosion process, and the applied stress seems increase the complexity and uncertainty of the ECN signal.     

Electrochemical characterisation of dental alloys: its possibilities and limitations

Dental alloys are metallic biomaterials which have a broad variation of composition compared to technical alloys. It is therefore in the interest of patients and technicians to conduct a good assessment of the electrochemical behaviour of dental alloys in order to collect information about their corrosion resistance. The purpose of this work was to demonstrate possibilities and limitations of two electrochemical techniques: the voltammetry of immobilised microparticles (ViMP) onto lead, and cyclic voltammetry measurements with the help of the mini-cell system (MCS). Based on fingerprints obtained from ViMP it was possible to analyse and differentiate the dental alloys. The results obtained by MCS were comparable with ViMP, but give a better understanding of the corrosion behaviour of the materials.     

干湿循环下混凝土中钢筋腐蚀的电化学检测

应用电化学噪声技术,结合电化学阻抗谱研究了干湿循环条件下3种不同pH值的3.5%NaCl溶液中混凝土钢筋的腐蚀过程.结果表明,钢筋的腐蚀分为3个阶段:钝化膜的溶解期、腐蚀活化期和腐蚀产物的累积期.在pH1的溶液中经过30个干湿循环后主要以均匀腐蚀为主,而对pH3和pH7溶液,则主要以点蚀为主,散粒噪声分析证实了混凝土中钢筋在强酸性溶液中更容易发生腐蚀.电化学阻抗谱分析也进一步说明了混凝土中钢筋的腐蚀经历了3个阶段:第1阶段Nyquist谱图中出现两个时间常数,高频区为混凝土层的容抗性质,低频区为钢筋与混凝土界面的电荷转移电阻;第2阶段,中频区增加一个时间常数,这与腐蚀产物的累积有关;第3阶段,随着腐蚀产物向混凝土中的扩散,中频区容抗弧有所减小,特别是pH1体系,中频弧几乎消失.SEM形貌表征观察到随着溶液酸度的增加钢筋表面的锈层明显增多.     

Electrochemical noise analysis of pitting corrosion of J55 steel in NaCl + NaHCO3 electrolytes

Electrochemical noise (EN) was used to study the pitting corrosion of J55 steel in NaCl/NaHCO₃ electrolytes. Below critical ratio for Cl^? to HCO^?, the corrosion rate increased with added NaCl, and conversely, decreased above that level. Also, the critical ratio was between 1 and 1.66. The PSD for potential and current noise were linear and rather gently sloped. J55 casing steel was quite sensitive to NaCl/NaHCO₃ electrolytes. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of electrochemical noise by means of bispectral technique

Nonlinear processes are often encountered in the practice of electrochemical and corrosion measurements. Especially, activation-controlled processes are inherently nonlinear. Taking into account investigations of electrode reactions, linear approximation is a popular approach. In this introductory paper, the possibility of extension of electrochemical noise (EN) measurements to the nonlinear regime is presented. Natural consequence of focusing on nonlinear processes is application of higher-order spectral techniques. Utilization of bispectral representation enables analysis of stationarity and linearity properties of EN. The authors present algorithm enabling assessment of both quantities and also exemplary analysis of noise generated during cathodic polarization, which is important for corrosion protection. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, 13–16 March 2005. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005.     

Electrochemical behavior of Ni-Al-Fe alloys in simulated human body solution

An investigation about the corrosion resistance of Ni-Al-Fe intermetallic alloys in simulated human body fluid environments has been carried out using electrochemical techniques. Tested alloys included 57 (wt%) Ni-(20 to 30) Al-(12 to 23) Fe using the Hank's solution because the high corrosion resistance provided by protective Al₂O₃ external layer. For comparison, AISI 316L type stainless steel has also been used. Electrochemical techniques included potentiodynamic polarization curves, electrochemical impedance spectroscopy, and electrochemical noise measurements. The different techniques have shown that these alloys showed a similar or higher corrosion resistance than conventional AISI 316L type stainless steel, and this corrosion resistance decreased as the Al content in the alloy increased. The alloys were susceptible to pitting type of corrosion on the interdendritic Ni-rich phases.     

Study of the electrochemical behaviour of a carbon steel electrode in sodium sulfate aqueous solutions using electrochemical impedance spectroscopy

The study of a plain carbon steel (AISI 1020) in Na₂SO₄ aqueous solutions at different concentrations was carried out by electrochemical impedance spectroscopy (EIS) in order to determine the corrosion mechanism and to obtain representative corrosion rates of the system. EIS was used to measure corrosion current densities at high concentrations in the range 0.1–1 wt% Na₂SO₄, but in the low concentration range, from 0.001 to 0.01 wt%, a scattered Nyquist plot was obtained. Other electrochemical techniques, such as polarization resistance (PR), Tafel plots and electrochemical noise (EN), were also used in this analysis. The charge transfer resistance was determined and compared with the PR and noise resistance. Electronic Publication     

Investigation of structure, stability, phase composition and magnetic ordering in ultrathin iron/nickel films

By thermal and chemical treatment of Langmuir-Blodgett (LB) films, oxidic and metallic Fe and Ni layers can be prepared. The films are characterised, where differences e.g. in the lateral homogeneity are found. The metallic Fe containing samples show a higher corrosion stability as compared with films prepared by other coating techniques. Mixed Fe/Ni oxidic and metallic layers, respectively, are prepared, where the Ni concentration in the oxidic films can be determined as a function of the ratio of initially transferred numbers of LB layers. The phase composition of the metallic Fe changes systematically with the Ni concentration.In partial fulfilment of his thesis     

Experimental correlation between metallographic evaluation and electrochemical noise in intergranular corrosion tests of aluminium alloys

In the present work, the correlation between the metallographic evaluation and electrochemical noise (EN) in intergranular corrosion (IGC) tests of aluminium alloy 2024‐T3 has been analysed. For this purpose, the influence of temperature and hydrogen peroxide concentration on the IGC attack has been studied. Similar IGC was observed between 20 and 40 °C, showing a low dependence with temperature (at least in this range). Hydrogen peroxide was seen to have a strong effect, leading to IGC activation when raising its concentration. The results of the detailed metallographic evaluation of the samples after the tests were analysed together with the EN measured during the tests. The averaged noise resistance was inversely proportional to the depths of the attacks, whereas the average of the parameter so‐called ‘Statistical Noise Power’ was directly related to the IGC degree. The metallographic evaluation and the EN showed a reasonable experimental correlation. Copyright © 2012 John Wiley & Sons, Ltd.     

铝合金表面电偶腐蚀与电子功函数的关系

铝合金中经常会引入一些第二相来改善其性能,第二相由于和铝基体的电位差不同,将会对铝合金的局部腐蚀产生重大的影响.为了揭示铝合金腐蚀的物理本质,本文利用基于密度泛函理论第一性原理的计算方法,详细计算了铝合金中一些主要第二相(Al_2Cu、Al_3Ti和Al_7Cu_2Fe)的多种晶面的电子功函数,分析了电子从各个晶面逸出的难易,求得了第二相与Al基体的本征电势差,我们发现不同的晶面暴露在合金最外层,会显著地影响本征电势差;即便是同一晶面,暴露在最外层的原子种类和构型不同,对腐蚀的影响也不一样.从电子的层面解释了电偶腐蚀发生的原因.     

EIS evaluation of protective performance and surface characterization of epoxy coating with aluminum nanoparticles after wet and dry corrosion test

The effect of addition of aluminum (Al) nanoparticles to epoxy coating on the ability to protect the carbon steel was studied by electrochemical impedance spectroscopy and focused ion beam-transmission electron microscopy. The EIS was conducted in 0.1?M NaCl solution after wet/dry cyclic corrosion test. The addition of Al nanoparticles increased the film resistance (R _f) and the charge transfer resistance (R _ct) of epoxy-coated steel. The surface analysis showed that uniform and fine Al–Fe complex oxide layers were formed acting as barrier layers that enhanced the corrosion protection of the epoxy-coated steel. It has been concluded that the Al nanoparticles had a beneficial role in improving the corrosion resistance of the epoxy-coated steel.     

Soft X-ray spectromicroscopy studies of pitting corrosion of reinforcing steel bar

Pitting corrosion of reinforcing steel bar (rebar) imbedded in concrete by chloride ions can cause concrete degradation. It is thus necessary to develop methods to mitigate concrete corrosion which could include using a protective polymer rebar coating. Corrosion studies of polyvinyl butyral-carbon black polymer-coated rebar using soft X-ray fluorescence (XRF) microprobe and micro-X-ray absorption near edge spectroscopy (μ-XANES) are reported in this study. After removal of the polyvinyl butyral-carbon black polymer coating, Fe Lα₁, Mn Lα₁, and O Kα₁ XRF maps were collected as well as Fe and Mn L₃-edge μ-XANES spectra from different regions across the whole rebar surface by collection of total electron yield (TEY) and partial XRF yield (PFY) spectra. The distribution of metallic Fe and Fe corrosion products was determined by analysis of the Fe XRF map. The μ-XANES spectra indicated a higher fraction of Fe (III) phases on the corroded rebar surface, while Fe (II/III) phases were the major corrosion products beneath the surface region. In addition, Mn (II) and Mn (III) were determined as the valence states of the manganese corrosion products.     

Influence of impurity elements on the corrosion of α-uranium surface: a density functional theory study

Journal of Radioanalytical and Nuclear Chemistry - Influence of substitutional Fe, Al and Mg atoms on the corrosion of α-U(110) surface was studied by DFT?+?U method. The...     

金属元素对Y沸石的液固相类质同晶取代

用(NH_4)_2TiF_6、(NH_4)_3ZrF_7和(NH_4)_3FeF_6为取代剂研究了Ti、Pe和Zr等杂原子对Y沸石的液固相类质同晶取代规律,发现Ti、Fe和Zr主要取代Y沸石中的A1,其取代程度取决于溶液中M/A1比,最高允许M/A1比与杂原子的半径和氟配合物的稳定常数有关。用XRD、IR、DTA和TPR表征了相对结晶度大于80％的杂原子Y沸石。Ti、Fe和Zr等杂原子进入Y沸石后,沸石的晶胞参数增大,热稳定性下降,红外反对称伸缩振动频率红移,且变化的程度与取代原子的半径和取代量有明显的对应关系,说明杂原子以四面体形式进入Y沸石骨架。     

Chemical transformations of Fe(III), Al(III), and Co(II) ions under cohydrolysis in coolants of nuclear power installations

The effect of dosing with aluminum salts of the water coolants of primary circuits at nuclear power installations on the radiation situation at their maintenance area via decreasing the 60Co content in the deposited activated corrosion products was examined. Potentiometric titration, gel chromatographic, and atomic absorption spectrometric techniques were employed for identifying the elemental composition and molecular-weight distribution of the hydrolytic polycondensation products yielded by cohydrolysis of the components of binary, Fe(III) + Co(II) and Fe(III) + Al(III), and ternary, Fe(III) + Al(III) + Co(II), mixed solutions (systems).