Atmospheric corrosion evaluation of galvanised steel by thin layer activation

The release of certain metals, such as zinc, from outdoor constructions due to atmospheric corrosion is of some concern. For risk assessments the evaluation of the amount of released metal is of importance. Various methods can be used to study the release of metals. These include those using radiotracers, such as thin layer activation (TLA). To verify the reliability of TLA with respect to conventional techniques in the evaluation of atmospheric corrosion, galvanised steel was exposed to a mild marine environment. The amount of zinc in the corrosion products, released through artificial leaching, at different time intervals was evaluated by TLA and atomic absorption spectroscopy (AAS). A good correlation between the results was found indicating the feasibility of TLA for these release studies.     

The use of thin layer activation in high-temperature cyclic oxidation studies

Thin layer activation (TLA) has been applied to a study of the high-temperature cyclic oxidation behaviour of pure and yttrium-implanted chromium, taking advantage of the high area selectivity of the technique.On pure chromium, two different sample areas, i.e. corners and the central part of a large surface area, were selected for activation. Due to this area selectivity, it was possible to distinguish the spallation behaviour of the oxide scale formed on flat from that formed on highly curved surfaces. In particular, the TLA data showed that the oxide scale formed during high-temperature cyclic oxidation near corners and edges was more prone to cracking and spallation.In the case of yttrium-implanted specimens, activation was performed only at the centre of the implanted zone, avoiding the distorting effect of the non-implanted parts of the sample. The area selectivity of TLA made it possible to study more accurately the beneficial effect of ion implantation on the cyclic oxidation behaviour than by conventional thermogravimetry. Due to the complementary character of TLA with respect to the conventional thermogravimetry, a more complete and better understanding of the cyclic oxidation performance of materials can be obtained.     

Surface modification of stainless steels: green technology for corrosion protection

Many methods of corrosion protection rely on toxic chemicals such as hexavalent chromium (Cr⁶⁺), which is the species responsible for protection in conversion coatings, anodizing baths and as a pigment in polymer coatings. Despite many attemps to replace Cr⁶⁺ and other harzardous chemicals in corrosion protection, very little progress has been made. Passive layers containing Ce and Mo have already been formed on materials such as A17075 and A12024, and their corrosion behaviour has been shown to improve by inhibition of both anodic and cathodic reaction. In this work the results of applying these coatings to SS304 and 316 will be presented. The layers were studied by electrochemical impedance spectroscopy (EIS), X-ray photo-electron spectroscopy (XPS), and the corrosion behaviour was followed by EIS and d.c. current methods.     

Dental amalgam – the effect of the technology of alloy powder preparation on the corrosion behaviour and the release of mercury

Dental amalgams are based on a broad spectrum of materials differing in their chemical composition, metallurgical treatment, and in the way the initial alloys powders are prepared. In addition to their chemical composition, amalgams based on various powders differ in both their microstructure and the amount of mercury needed for preparation. All these facts may affect electrochemical processes occurring during their interaction with oral fluids, and also mercury release. While verifying the effect of the technology used for the preparation of the high‐copper ternary alloy powder on the properties of resulting amalgams, this study aimed at the mechanism of their interaction with a model saliva solution as well as mercury release was included. Measurements were done in a model saliva solution using standard electrochemical methods and exposition measurements. The interaction of individual types of amalgams with artificial saliva did not reveal any significant differences. The free corrosion potential of all these amalgams in an aerated solution settled in the range of values in which tin oxidation, resulting in a layer of insoluble corrosion producsts, turned out to be the dominant anodic process. The rate of mercury release was the lowest for amalgams based on a gas‐atomized alloy. The highest rate of mercury release, and also its dependence on time, was exhibited by lathe‐cut powder based amalgam. In addition to different volume fraction of the Ag‐Hg phase and the level of its tin alloying, this different behaviour may be explained by differences in the rate at which a layer of tin corrosion products acting as a barrier to mercury release is formed.     

机械镀锌镀层钝化与耐蚀性能研究

    对机械镀锌层分别用三价铬、稀土和六价铬进行了钝化处理,利用盐雾试验和电化学测试对不同钝化膜的耐蚀性与电化学行为进行了比较研究.盐雾试验结果表明,稀土与三价铬钝化处理的效果均已超过传统的六价铬钝化,比六价铬钝化膜的耐蚀性提高了一倍以上;稀土钝化膜的耐蚀性最好,三价铬钝化膜的耐蚀性仅次于稀土钝化膜的.电化学测试表明,三价铬、稀土和六价铬钝化膜都能够不同程度地抑制腐蚀的阴极电极反应,抑制阴极反应程度最大的是稀土钝化膜,其次是三价铬钝化膜,最小的是六价铬钝化膜.三价铬与稀土钝化工艺的环保和良好的防腐效果使其具有良好的应用前景.     

海水中带锈Q235钢腐蚀电化学参数测定

利用失重法和电化学方法对在海水中浸泡不同时间的Q235钢电极的腐蚀行为和腐蚀速率规律进行了研究。结果表明,对于长期浸泡的Q235钢电极,失重法和电化学方法得到的腐蚀速率结果存在很大差异。利用XRD测定了长期浸泡后锈层成分的变化,发现长期浸泡Q235钢电极锈层中的电化学活性成分β-FeOOH在测试过程中发生还原反应,导致利用电化学方法测得的Q235钢腐蚀速率大于失重法的结果,并且随浸泡时间的延长,这一偏差增大。对长期浸泡Q235钢电极进行电流密度为-25 μA/cm²阴极恒电流预极化处理后发现,随着浸泡时间的延长极化时间也延长,同时,经过预处理之后的Q235钢电极电化学方法测得的腐蚀速率与失重法的结果具有一致的变化规律,表明施加合适的阴极极化预处理能够减小电化学方法与失重法测试结果的偏差。     

A mathematical model for electrochemical chloride removal from marine cast iron artifacts

The aim of this article was to theoretically study diffusion and migration of chlo-ride ions during electrochemical chloride removal. The proposed model would enable optimization of its application by predicting the optimal treatment time and current combination. A mathematical model for simulating the transport behavior of chloride ions was developed by consideration of diffusion and migration of chloride ions when a constant DC current density was applied through the marine cast iron artifacts. The corresponding tests were conducted to validate the mathematical model. This model predicted the data of the extraction ratio of the chloride ion that correlated satisfac-torily with the experimental values. An important issue in electrochemical chloride removal was to understand how chloride ions moved, taking account of diffusion and migration of chloride ions and the release of binding chloride ions. The effects of the treatment time, externally applied current density, chloride diffusion coefficient, and rate constant of release of binding chloride ion on chloride removal are studied. The specific quantitative details applied to one-dimensional model were discussed here. This article has proposed a mathematical model for the first time, which was showed to be a useful tool that can reveal the ionic transport mechanism and optimize the application during electrochemical chloride removal.     

Al合金点腐蚀及研究方法

综述近年来国内外有关Al合金点腐蚀的研究概况.包 括特征电位的研究、点腐蚀发生发展机理的研究和缓蚀剂缓蚀机理研究等.侧重介绍近几年 在Al合金点腐蚀研究中具有空间分辨度的原位研究技术.     

金属大气腐蚀实验技术进展

综述了金属大气腐蚀的实验方法和分析手段及各种方 法的优缺点，探讨了金属大气腐蚀研究的发展趋势.     

Corrosion-induced copper runoff from naturally and pre-patinated copper in a marine environment

Corrosion-induced copper runoff has been monitored for copper sheet, naturally patinated copper and pre-patinated copper, with and without surface treatments, in a marine environment during one year. The study comprises solution measurements on total copper runoff rates, sulphates and chlorides released from the patina, and parallel surface analytical studies on patina formation, combined with electrochemical impedance measurements on changes in barrier properties during exposure. Bioassay tests and model predictions were applied to elucidate copper bioavailability at the immediate release situation. The runoff rate of copper was significantly lower compared to the corrosion rate throughout the exposure period. At comparable rain quantities, copper runoff rates were significantly lower at the marine site compared to similar data obtained in an urban environment. The bioavailable concentration of released copper was significantly lower compared to the total copper concentration.     

有机涂层防护性能的电化学研究进展

曝晒、盐雾、浸泡、干湿循环、老化等传统的有机涂层防护性能研究方法,因测试周期长,测试结果多为定性分析,不能使涂层材料进行快速检验而投入评估使用.正是由于传统测试方法存在许多局限性,故综述了稳态电化学测试方法和暂态电化学测试方法这两种新技术在有机涂层防护性能中的应用与进展.介绍了动电位极化曲线法、极化电阻法等稳态电化学测试方法,这类方法主要反映涂层的极化电阻和腐蚀速度,并且方法简单,可直接分析实验数据,被广泛应用于有机涂层的失效分析中.而暂态电化学测试方法主要包括电化学阻抗法(EIS)、局部阻抗法(LEIS)、扫描Kelvin探针法(SKP)及电化学噪声(EN)等,主要用于研究涂层防护机制和局部缺陷.目前,在有机涂层防护性能和机理研究中,应用最多的是电化学交流阻抗法.丝束电极法(WBE)、扫描电化学显微镜(SECM)以及原子力显微镜(AFM)用于研究金属/涂层界面物理化学变化规律.阐述了上述方法在涂层防护研究中的应用成果及其优势和不足,指出对于深层次的涂层防护研究,需要应用多种测试手段,从不同的角度和方面综合分析,全面评估涂层的使用寿命.     

Surface characterization of AISI 316L biomaterials obtained by electropolishing in a magnetic field

The paper deals with comparison of the results obtained by electropolishing AISI 316L surfaces in an externally applied magnetic field with those of a standard electropolishing process. All electrochemical investigation methods, electrochemical impedance spectroscopy (EIS), polarization curve measurements, and surface analytical methods such as surface roughness measurements and scanning electron microscopy were carried out to determine the efficacy of electropolishing in a magnetic field.     

Test protocols for migrating corrosion inhibitors (MCI®) in reinforced concrete

Corrosion induced deterioration of steel reinforcement (rebar) in concrete has increasingly become a greater world‐wide concern. This insidious dilemma focuses on the potentially dubious structural integrity of many concrete structures. The steady rise of rebar corrosion and the eventual deterioration can be directly related to several influential factors, some of which include; poor quality construction materials, the increased use of de‐icing salts, severe marine environments and increased atmospheric contaminants, such as carbon dioxide. Over the years various methods have been developed to protect either the rebar or the concrete. Today, the most recent emerging corrosion protection technology is that of Migrating Corrosion Inhibitors (MCIs). Recently, improved test methodologies have been developed which can better assess the effectiveness of corrosion inhibitors. Several of these recent electrochemical and non‐electrochemical test methods were utilized to measure the effects of migrating corrosion inhibitors. This paper includes an explanation of these test methods and presents an overview of the test results.     

Polyterthiophene as an electrostimulated controlled drug release material of therapeutic levels of dexamethasone

Polyterthiophene has been investigated as a substrate for the controlled release of dexamethasone, a synthetic glucocorticoid anti-inflammatory drug, which is widely used to help reduce inflammation in the central nervous system. Dexamethasone was incorporated into the polymer as an anionic dopant during electrochemical polymerisation from water–acetonitrile solutions. Optimal polymer synthesis conditions were established to yield reproducible dexamethasone release profiles into a simulated physiological receiving solution. A homogeneous morphology of the polyterthiophene substrate with minimal extraneous features was observed to be critical for achieving reproducibility of release. Release profiles were established using a range of electrochemical stimulation protocols over a 24 h time period. The amount of dexamethasone released from the polyterthiophene under all electrostimulation protocols was at therapeutically relevant levels, with a maximum release of ～80 μg/cm² achieved when the polymer film was in a reduced state. The oxidation state of the polyterthiophene was found to be critical for controlled release of the dexamethasone. Polyterthiophene doped with dexamethasone was observed to auto-reduce when placed into the receiving solution. As a consequence, no significant difference was observed between the unstimulated (auto-reduced) polymer and the electrochemically reduced polyterthiophene. By electrochemically holding the polyterthiophene in the oxidised state, the rate of release of dexamethasone was significantly impeded with ～40 μg/cm² released over a 24 h period.     

Preparation of LiNi_(1-y)Co_yO_2 in certain oxygen pressure

1　INTRODUCTIONLi ionbatteryisthenewlydevelopedrecharge ablebatterysubsequenttoCd/NiandMH/Nibat tery .Itshighenergypropertyisnotonlyfitforthepowersupplyofsmallscaleelectricproductdevelop ingattopspeed ,butalsofitforthepowersupplyofthelargescalemotivepowertooltoavoid pollutingtheenvironment .Thepreparationofcathodematerialisthekeylinksforthedevelopmentoflithiumionbattery .Atpresent ,thecathodematerialsusedinlithiumionbatteryareLiCoO2 ,LiNiO2 ,LiMn2 O4 andtheirderivatives .Amongthem ,…     

Stress distributions due to hydrogen concentrations in electrochemically charged and aged austenitic stainless steel

As a result of hydrogen concentration gradients in type austenitic stainless steels, formed during electrochemical charging and followed by hydrogen loss during aging, at room temperature, surface stresses were developed. These stresses were measured by X-ray technique and the crack formation thus induced could be studied using equilibrium stress equations. After various electrochemical charging and aging times, X-ray diffraction patterns obtained from samples indicated that the reflected and broadened diffraction peaks are the result of the formation of a non-uniform but continuous solid solution in the austenitic matrix. Since both hydrogen penetrations during charging and hydrogen release during aging are diffusion controlled processes and huge hydrogen concentration gradients in the thin surface layer, at depths comparable with the depth of X-ray penetration, are observed. The non-uniform hydrogen concentration in the austenitic matrix, results to the non-uniform expansion of the atomic microstructure and latter inevitably leads to the development of internal stresses. The internal stresses development formulae’s are very similar to those relating to non-uniform heating of the materials, where thermal stresses appear due to non-uniform expansion or contraction. The relevant well developed theory is applicable in our case of non-uniform hydrogen concentrations in a solid solution of electrochemically charged and aged austenitic matrix. A few cracks were present on the surface after some minutes of electrochemical charging and the severity of cracking increased as hydrogen was lost during subsequent aging. This is consistent with the expectation of high compressive stresses in the bulk of the specimen during charging and high tensile surface stresses (at the level of 1 × 10¹¹ Pa) during the aging process. These stresses can induce the formation of surface cracks during the aging process after electrochemical charging in the AISI 316 stainless steel. Electrochemical charging of AISI 316 stainless steel led to surface cracking that was both in the types transgranular and intergranular.     

防锈油膜失效期间的电位波动现象

采用丝束电极研究了防锈油膜失效期间的电位波动现象。研究表明，防锈油膜具有自修复能力，具这种自修复能力与油溶性缓蚀剂的浓度和种类有关；采丝束电极研究和评介防锈油膜的自修复能力是可行的。     

Change from a bulk to a surface coupling mechanism in the electrochemical polymerization of thiophene

The electrochemical polymerization of thiophene has been studied by spectrovoltammetric, spectrogal vanostatic and electrochemical quartzcrystal microbalance (EQCM) techniques. Experimental support was found for a change from a bulk to a surface coupling mechanism during the process at weakly adsorbing electrodes like indiumtin oxide (ITO). This conclusion has gained further proof from experiments in connection with the effect of a strong deprotonating agent (DBN). It was observed that the solution phase inhibitor is inefficient when it was added only during the process, when the surface had already been covered by a prepolymerized layer. The film formation undisturbed by the late addition of the inhibitor was illustrated by evidence obtained from spectroelectrochemical and EQCM measurements.     

Co2 corrosion inhibition of X-120 pipeline steel by a modified imidazoline under flow conditions

A study of the effect of flow conditions on the performance of a carboxyethyl-imidazoline as CO₂-corrosion inhibitor for API X-120 pipeline steel has been evaluated. Testing techniques include polarization curves, linear polarization resistance, electrochemical impedance spectroscopy and electrochemical noise measurements under stirred conditions (0, 250, 500, 1000 and 2500 rpm). All these techniques show that for the uninhibited solution, corrosion rate increases with an increase in the rotation speed, but for the inhibited solution, the lowest corrosion rate is obtained at 500 rpm, and it increases at lower or higher rotation speeds.     

海水缓蚀剂作用于预腐蚀表面的缓蚀效果评价

应用不同的失重方法对表面洁净和有预腐蚀的907A钢在海水缓蚀剂介质中的腐蚀行为进行了研究，通过缓蚀效率比较，评价了多元醇磷酸酯类缓蚀剂作用于不同表面状况下的907A钢的缓蚀效果，同时利用电化学阻抗谱（EIS）测量得到界面电化学参数，解释了这种缓蚀行为的差异。结果表明：在静止海水中，缓蚀剂对洁净表面907A钢试样的缓蚀效率远远高于表面有预腐蚀的试样；而在流动海水中，缓蚀剂对预腐蚀试样却具有更高的缓蚀效率，907A钢表面状况和环境介质的流速明显改变了缓蚀剂的缓蚀效果。