锌铝基重防腐涂料的开发与应用

根据钢结构特殊部位重防腐需要,以片状锌铝粉为基本填料,改性树脂为成膜物,开发出锌铝基重防腐涂料。对该涂料的防护性能和成本进行分析研究,结果表明:锌铝基涂料成膜后,其自腐蚀电位为-980 mV,可以对基体提供良好的牺牲阳极保护,其耐盐雾寿命为1 964 h。该锌铝基涂料与现有的锌铝基涂料相比具有明显的成本优势。     

镁合金电沉积镍形成机理及电镀工艺的研究

分析了浸锌层的作用机理,利用恒电势下电流密度随时间的变化和开路电势随时间变化的曲线,研完了镍在浸锌层上的形成机理.研究发现:镍的电沉积形核过程为连续形核,超电势增加时,晶核数迅速增加;镍层的生长过程遵循VolmerWeber模式;浸锌层能明显改善镀层结合力.在镀镍溶液中加入晶粒细化剂,细化了镀层晶粒,提高了镀层性能.X射线衍射表明:晶粒细化剂加入后,镍层晶粒明显细化,平均柱径约为26 nm,镍层表现为(111)择优取向.纳米晶镍层具有优良的性能,15μm厚的镀层24 h中性盐雾实验的保护等级为9级,热震和划痕试验表明结合力良好.     

The production of oxalic acid from CO2 and H2O

Oxalic acid has been prepared on a preparative scale in an undivided cell with sacrificial anodes and an aprotic electrolyte. Optimum current efficiencies (>90%) have been obtained in cells with zinc anodes, stainless steel cathodes and acetonitrile with tetrabutylammonium perchlorate as the electrolyte. Micro-pilot experiments revealed that a continuous electrochemical cell can be set up and that the reaction product can be removed by filtration. A complete process is designed by a combination of the oxalic acid production with a zinc electrolysis. No unwanted by-products appear, which is recently of increasing importance. Economic consideration shows that the process may become interesting in the future.     

铝粉的质量分数对达克罗涂层耐蚀性的影响

以片状锌粉和片状铝粉为原材料制备不同铝的质量分数的达克罗涂层.通过盐雾试验和电化学方法评价涂层的耐蚀性.结果表明:随着铝的质量分数的增加,达克罗涂层逐渐变得光亮、细致、光滑;涂层的自腐蚀电位依次升高,铝的质量分数50%以上的涂层,不具备牺牲阳极性能;涂层耐盐雾腐蚀时间的变化趋势与涂层牺牲阳极作用持续时间的变化趋势一致,均先升后降,在铝的质量分数为15%处达到极大值.     

涂层-牺牲阳极联合保护在水工金属结构防腐中的应用

水下或地下金属结构的腐蚀属电化学反应。其防腐措施通常有：涂漆、喷锌和外加阴极电流,这几种方法都存在不同的缺点,文中提出将涂漆和牺牲阳极同时用于水工金属的防腐。实践证明：联合保护法经济、防腐效果好。     

Surface treatment of carbon steel substrates to prevent cathodic delamination

Steel structures immersed in seawater are protected from corrosion using cathodic protection systems (sacrificial anodes or impressed current), by paint coatings or by duplex systems in which cathodic protection hinders corrosion at coating's failure sites. The main problem related to those duplex systems is how to avoid cathodic delamination due to the alkalinity generated at cathodic sites.The present paper analyses the effectiveness of red mud suspensions as pre-treatment to avoid cathodic delamination. The study was conducted using mainly electrochemical impedance spectroscopy (EIS). The evolution of the electrode potential with immersion time was also recorded because it concerns the practical aspect of current density necessary to reach the protection potential.The study shows that red mud pre-treatments are effective in avoiding coating's delamination.     

Electrocarboxylation of benzyl chlorides at silver cathode at the preparative scale level

The electrocarboxylation of benzyl chlorides to the corresponding carboxylic acids performed at silver cathodes was investigated both theoretically and experimentally in order to find the influence of the operative parameters on the selectivity and on the Faradic efficiency of the process. Theoretical considerations were confirmed by the electrocarboxylation of 1-phenyl-1-chloroethane performed in undivided cells equipped with sacrificial anodes both in a bench-scale electrochemical batch reactor and in a continuous batch recirculation reaction system equipped with a parallel plate electrochemical cell. Selectivity and Faradic yields higher than 80% and 70%, respectively, were obtained by working under anhydrous conditions both under amperostatic and potentiostatic alimentation at appropriate values of either current density or applied potential.     

大型浮顶油罐温度场数值模拟

大型浮顶油罐温度场的准确预测对于原油的战略和商业储备均有着重要的意义。油罐中温度场受大气温度、罐壁保温层厚度与热导率、太阳辐射强度、罐底土壤物性、油品物性等因素的影响。本文考虑以上众多因素的影响，建立了二维大型浮顶油罐温度场预测模型，开发了将浮舱区、油品区、土壤区及罐壁和保温层耦合求解的SIMPLE算法程序。研究了太阳辐射、保温层厚度等因素对油品温度的影响，并将计算结果与现场测试数据进行了对比，发现本模型的预测结果与实验结果吻合良好。     

Anticorrosion properties of an epoxy zinc-rich composite coating reinforced with zinc,aluminum, and iron oxide pigments

The effects of lamellar aluminum (Al) and micaceous iron oxide (MIO) pigments on the anticorrosion properties of an epoxy zinc-rich coating were studied. To this end, the epoxy zinc-rich coatings containing 70% w/w spherical Zn particles, 60% w/w Zn + 10% w/w MIO, and 60% w/w Zn + 10% w/w Al were prepared. The electrochemical noise (ECN), potentiostatic polarization technique, and salt spray test were employed in order to investigate the anticorrosion performances of the zinc-rich coatings. The zinc-rich coatings morphologies were studied by scanning electron microscope (SEM) before and after the salt spray test. The open-circuit potential values were also measured at different immersion times. Results showed that MIO particles could enhance the cathodic protection duration of the zinc-rich coating by enhancing its barrier properties and reducing the zinc particles oxidation rate. It was also shown that Al particles reduced zinc-rich coating sacrificial behavior at short immersion times and increased it at long immersion times. Unlike MIO particles, Al particles behaved both as barrier and sacrificial pigment.     

高性能牺牲阳极材料的研究

研究了四种新型铝合金牺牲阳极并测试了其电化学性能以及电位与时间的关系,绘制了极化曲线。实验结果表明:电流效率均高于85%,电位随时间变化不大,具有良好的活性、组织结构均匀。该材料用于海水中钢铁的阴极保护,效果良好。     

A tartrate-based alloy bath for brass-plated steel wire production

The plating of brass on steel from a tartrate based alloy bath has been studied using electrochemical methods and surface analysis techniques. The coating composition obtained using both direct current (d.c.) and pulsed current (p.c.) electrolysis was examined for a variety of temperatures, current densities and bath compositions. The dissolution process of a suitable composition of brass anodes was studied using small amounts of nitrate as depolarizing agent. Tests in a pilot plant showed that when electrolysis is carried outin continuo the coating composition remains constant with time (±1%). Tests were performed at cathode current densities of industrial interest (20–30 A dm^–2). The Auger and XPS analyses combined with Ar⁺ etching indicated a homogeneous composition throughout the coating.     

金属基有机硅树脂涂层复合材料的导热性能

以锌粉为导热填充剂对环氧有机硅树脂进行改性,考察了改性环氧有机硅树脂涂层干膜中锌粉含量对涂层导热系数的影响,分析了涂层厚度对碳钢基材导热性能的影响. 结果表明,环氧有机硅树脂涂层的导热系数约为0.19 W/(m?K),其耐温能力在200℃以上,可保证涂层在中低温烟气余热回收换热器表层长期工作而不发生任何热反应;添加锌粉可改善环氧改性有机硅涂层的导热性能,涂层干膜锌粉25wt%时,涂层材料导热系数达0.35 W/(m?K),较未添加锌粉时增大了84%. 复合材料的导热系数随涂层厚度增加而下降,无涂层的碳钢导热系数为47.59 W/(m?K),涂层厚度为200 ?m时,导热系数降至34.33 W/(m?K).     

Thermal conductivity of intumescent coating char after accelerated aging

This paper presents the results of an experimental and numerical simulation study to obtain thermal conductivity of intumescent coating after accelerated aging. Two types of intumescent coating were used. The main objective of this research was to check the accuracy of a thermal conductivity model for the fully expanded intumescent coating char, which was assumed to depend on the expansion thickness and the bubble size and distribution. By using the model and the measured expanded thicknesses and average bubble diameters for the two types of intumescent coating after different cycles of accelerated aging, the intumescent coating insulated steel plate temperatures were numerically calculated and compared with measured results. The agreement has been found to be generally satisfactory, suggesting that the thermal conductivity model is acceptable. The measured results of intumescent coating expanded thickness and bubble size show that aging has two detrimental effects on the insulation performance of intumescent coating: reducing the expansion thickness and increasing the bubble size, both leading to increased thermal conductivity. Copyright © 2012 John Wiley & Sons, Ltd.     

A mathematical model for the internal cathodic protection of cylindrical structures by wire anodes

The applicability of a two-dimensional mathematical model of the impressed current cathodic protection (CP) system of the interior wall of a cylindrical structure was investigated. The modelled system was an axisymmetric cylindrical column filled with electrolyte with a wire anode running along its entire length and displaced from the column axis. Model inputs included anode and cathode dimensions, the anode-to-cathode distance, the electrolyte conductivity and limiting current density of oxygen reduction. A semi-analytical solution to the Laplace equation was used to compute the distribution of electrical potential. From these results, the nonuniform current density distribution was obtained to a first approximation by entering the computed values of the position-dependent cathode polarization potential into the nonlinear experimentally obtained polarization expression. The experimental electrical potential distribution compared well with that predicted by the model. Results showed the possibility of overprotection occurring in the system. The mathematical analysis was also extended to the case of a system with two wire anodes.     

High capacity alkaline super-iron boride battery

A high capacity alkaline redox storage chemistry is explored based on a novel Fe⁶⁺/B²⁻ chemistry. The alkaline anodes based on transition metal borides can deliver exceptionally high electrochemical capacity. Over 3800 mAh/g discharge capacity is obtained for the commercial available vanadium diboride (VB₂), much higher than the theoretical capacity of commonly used zinc metal (820 mAh/g) alkaline anode. Coupling with the super-iron cathodes, the novel Fe⁶⁺/B²⁻ battery chemistry generates a matched electrochemical potential to the pervasive, conventional MnO₂–Zn battery, but sustains a much higher electrochemical capacity. Stability enhancement of super-iron boride battery is also studied. A zirconia coating effectively prevents both the decomposition of boride anodes and the passivation of Fe(VI) cathodes, and sustains facile both anodic and cathodic charge transfer. Reversibility of boride anodes is demonstrated with TiB₂ and VB₂. It is shown that these two boride anodes exhibit the reversibility in a certain extent.     

Electrophoretic deposition of bioactive glass nanopowders on magnesium based alloy for biomedical applications

To slow down the initial biodegradation rate of magnesium (Mg) alloy, crystalline nano-sized bioactive glass coating was used to deposit on micro-arc oxidized AZ91 samples via electrophoretic deposition (EPD). Zeta potential and conductivity of the bioactive glass suspension were characterized at various pH values to identify the most stable dispersion conditions. The bone-bonding properties of bioactive glass coated samples were evaluated in terms of apatite-forming ability during the immersion in simulated body fluid (SBF) solution. Results revealed that the ability to form a bioactive glass coating via EPD was influenced by the degree of its crystalline phase composition. Moreover, the potentiodynamic polarization tests recorded significant drops in corrosion current density and corrosion rate of the coated samples which implies a good level of corrosion protective behavior. These preliminary results show that this process will enable the development of Mg implants in the later stage of bone healing.     

AZ91D镁合金电镀Al-Zn复合镀层及耐蚀性研究

为了提高AZ91D镁合金的抗腐蚀性能,在其表面电镀Al-Zn复合镀层.研究了镀层的物相组成、微观形貌、结合力及抗腐蚀性能.结果表明,镀铝为中间层能得到较好的组织和性能,镀层表面为纯锌,镀Zn层分布致密均匀,镀锌层约6μm,中间铝层约4μm且组织疏松;电流密度3.5 A/dm2、电镀时间1 min时镀层具有较好的结合力与...     

Corrosion resistance of phosphate coatings obtained by cathodic electrochemical treatment: Role of anode–graphite versus steel

The formation of phosphate coatings by cathodic electrochemical treatment using graphite and steel anodes and evaluation of their corrosion resistance is addressed in this paper. The type of anode used, graphite/steel, has an obvious influence on the composition of the coating, resulting in zinc–zinc phosphate composite coating with graphite anode and zinc–iron alloy–zinc phosphate–zinc–iron phosphate composite coating with steel anode. The corrosion resistance of the coating is found to be a function of the composition of the coating. The deposition of zinc/zinc–iron alloy along with the zinc phosphate/zinc and zinc–iron phosphate using graphite/steel anodes has caused a cathodic shift in the E_corr compared to uncoated mild steel substrates. The i_corr values of these coatings is very high. EIS studies reveal that zinc/zinc–iron alloy dissolution is the predominant reaction during the initial stages of immersion. Subsequently, the formation of zinc and iron corrosion products imparts resistance to the charge transfer process and increases the corrosion resistance with increase in immersion time. The corrosion products formed might consist of oxides and hydroxychlorides of zinc and iron. The study suggests that cathodic electrochemical treatment could be effectively utilized to impart the desirable characteristics of the coating by choosing appropriate anode materials, bath composition and operating conditions.     

聚合物基镁离子固态电解质的研究进展Q

镁离子电池因其比容量高、资源丰富、环境友好、安全性高(无枝晶)等优势,在储能电池领域脱颖而出.然而,镁金属负极在液态电解质中易钝化,导致其电化学性能不佳.因此,开发高效适用的固态电解质对实现高性能、实用化镁离子电池至关重要.聚合物电解质具有优异的机械稳定性、电化学稳定性、热稳定性且离子电导率高、成本低.但镁离子较高的电荷密度和较强的溶剂化作用限制了其在固态电解质中的解离与扩散.从纯固态聚合物电解质、凝胶聚合物电解质、复合聚合物电解质3个方面综述了国内外聚合物基镁离子固态电解质的离子电导率对解决镁金属负极钝化效应的贡献及其应用研究进展,指出聚合物基镁离子固态电解质当前面临的挑战并对其研究方向进行了建议和展望.     

Electrochemical impedance behavior of graphite-dispersed electrically conducting acrylic coating on AZ31 magnesium alloy in 3.5 wt.% NaCl solution

The paper deals with understanding the electrochemical impedance behavior of (a) chromate coating (b) electrically conducting polymer coating and (c) polyurethane coating under different combinations applied over AZ31 magnesium alloy in an effort to develop a conducting organic coating that can offer corrosion protection as well as electrical conductivity. The study indicates that dispersion of graphite in acrylic coating though significantly brings down the electrical resistance; application of such a coating on the magnesium alloy does not offer good resistance against corrosion. In order to gain both the corrosion resistance as well as electrical conductivity an intermediate coating such as polyurethane needs to be provided. The paper discusses the electrochemical impedance behavior of the above coatings.