杂散电流对接地材料在陕北土壤模拟溶液中腐蚀行为影响

采用自行设计的杂散电流模拟装置,测试了距离杂散电流源不同距离的纯锌、纯铜和锌/铜耦接结构在陕北土壤模拟溶液中的电位和腐蚀电流,并结合电化学阻抗谱对接地材料腐蚀行为进行分析.研究发现接地材料纯锌表面存在明显的由阴极区向阳极区的过渡,阳极区的试样腐蚀严重;纯铜表面发生电化学反应的阻抗明显高于纯锌,在存在杂散电流的介质中具有更好的耐蚀性;锌作为牺牲阳极与纯铜接地材料耦接后,会使纯铜表面电位整体负移,原来位于杂散电流流出区域的纯铜也进入阴极区受到保护.      

通过化学分析预测锌基涂层耐蚀性能的专家系统

本研究旨在开发一种用于预测锌基涂层耐腐蚀性的通用方法,其可以表示为加速盐雾试验中的总质量损失。本方法仅基于三个分析参数,即锌、铝和镁的总涂层质量。这种限制的原因是这三种参数可能通过在线分析获得。然后,预测的耐腐蚀性被包括在一个过程/质量控制系统。加速腐蚀试验在布雷斯特的Swerea KIMAB IC（腐蚀研究所）以及比利时的冶金研究中心（CRM）进行。试验按照雷诺ECC1试验D172028/--C（12周）以及CRM研发的加速循环腐蚀试验进行。根据总质量损失情况,原材料被分为四个耐腐蚀级别。所有腐蚀试验都清晰、充分地说明了元素镁和铝的正面影响。对于涂层中大多数这些元素来说,元素镁和铝的影响比单独元素锌的影响大很多。因此,引入了一个新的量,叫做"等量元素锌涂层重量"。此量与锌、铝和镁的涂层重量线性相关。使用专家系统开发了一种用于预测耐腐蚀性的模型,此模型基于回归分析和"决策树"算法。根据上述提及的三个分析参数（即锌、铝和镁的总涂层质量）,可以使用开发的模型准确对27种材料中的25种进行分类。总之,即使是在线状态,这种方法也有可能准确预测出腐蚀行为。出于材料研发的目的,还扩展了专家系统使其包括其他分析参数。     

Improvement of the Galvanized Coating Quality of High Strength Dual Phase Steels by Pre‐Electroplating Nickel Layer

Galvanized dual phase steel sheets are used extensively in the industrial applications because of their excellent mechanical properties and superior corrosion resistance, but the segregation of alloying elements and the formation of oxides on the steel surface often have a deleterious effect on coating adhesion during the galvanizing process. In order to improve the coating quality, a nickel layer was pre‐electroplated on the steel substrate before galvanizing and it's found that there is an improvement in the coating quality. The coating microstructures were investigated by scanning electron microscopy together with energy dispersive X‐ray spectroscope, glow discharge optical emission spectroscope and X‐ray diffractions. The experimental results show that the compact Ni₃Zn₂₂ intermetallic layer formed at the zinc/nickel interface during the galvanizing process, prohibiting the nucleation and the growth of the ζ‐Zn phase layer and resulting in the improvement of the zinc coating adhesion.     

Effect of samarium on microstructure and corrosion resistance of aged as-cast AZ92 magnesium alloy

The effects of samarium（Sm） on microstructure and corrosion resistance of AZ92 magnesium alloy were characterized and analyzed by scanning electronic microscopy, X-ray diffraction, mass loss test, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy and potentio-dynamic polarization test. The results showed that the added Sm could promote continuous precipitation of β-Mg17Al12 phase in grains, and meanwhile restrain discontinuous precipitation of the same phase along the grain boundaries. Thus, the precipitations distributed more uniformly in the aged AZ92 magnesium alloys. When the content of Sm was 0.5 wt.%, the corrosion resistance of aged AZ92 alloy tended to be the best, which was due to the β-phase distributes more homogeneous reducing the galvanic corrosion. The corrosion product film had more integrality and compactness than AZ92 alloys without Sm. However, it resulted in worse corrosion resistance of AZ92 alloy because of the formation of mass cathodic Al2 Sm phase coming from excess Sm in AZ92 alloy.     

The simultaneous electrowinning of manganese dioxide and zinc from purified neutral zinc sulphate at high current efficiencies

A process that enables electrolytic-grade manganese dioxide and zinc to be electrowon simultaneously at high anodic and cathodic current efficiencies from purified neutral leach liquor from a zinc plant is described. Experimental results that show the effects on the anodic and cathodic current efficiencies of temperature, anodic and cathodic current densities, initial sulphuric acid concentration, initial zinc-ion concentration, initial manganous-ion concentration, and addition of a polyelectrolyte smoothing agent are presented and discussed.     

A Novel Characterization Technique to Determine Pore Susceptibility of Alloying Elements in Aluminum Alloys

An investigation into the effect of ternary alloying element additions such as copper, magnesium, manganese, zinc, and nickel on pore formation in cast Al-12.6-wt pct Si eutectic alloy by employing a novel pore characterization technique is reported here. In this approach, the low-pressure testing method was combined with the metal foam manufacturing technique of intentionally adding TiH₂, which enhances hydrogen pore formation and offers a method to distinguish the effect of individual alloying elements on hydrogen porosity formation.     

Surface and Coating Analysis of Press‐Hardened Hot‐Dip Galvanized Steel Sheet

The use of continuous galvanized steel sheet as feedstock material for press hardening leads to components of very high strength levels with classical cathodic corrosion protection. The present work provides an insight into this technology with special focus on surface oxidation and intermetallic phase formation during the austenisation process. For that reason hot dipped galvanized 22MnB5 steel sheets, with a blank thickness of 1.5 mm and an average coating weight of 70 g m^?2, were annealed in a temperature range of 400–900°C in steps of 50°C without soaking before quenching in water. Surface and cross‐cuts were analyzed by SEM, EDX, and XRD to illustrate the phase formation and the surface changes during thermal treatment. Corrosion behavior was also studied based on electrochemical investigations and an accelerated, cyclic, automotive corrosion tests called VDA, which is a mixture of salt spray test and alternating climate test. It was found that austenisation of galvanized steel sheet causes a significant change of the coating. The generated coating still offers cathodic protection for the steel substrate and has higher corrosion resistance than standard galvanized steel sheet. Surface oxidation also occurs during the press hardening process leading to a surface covered with successively arranged layers of Al₂O₃ and ZnO, containing also further oxidized alloying elements.     

Magnesium, calcium and zinc levels of maternal and fetal tissues in magnesium deficient rats

The interaction of magnesium with two other mineral elements, calcium and zinc, was studied in maternal tissues and fetuses of pregnant rats fed a magnesium deficient diet throughout gestation. Reduction in maternal femur magnesium and a trend for increased kidney calcium reflected the dietary magnesium deficiency. In fetuses, however, total magnesium content was reduced and , in addition, fetal zinc content was also lower than normal in the group most severly deficient in magnesium. The possible interpretation of this magnesium-zinc interaction is discussed.     

Use of Calcium in Alloys: From Modifying to Alloying

Calcium is one of the most widespread and, consequently, low-cost metals on Earth. It has been applied for a long time in modifying and alloying alloys of heavy metals, in particular, lead and copper. It is used as a modifier in cast irons and steels. Calcium began being applied for alloying light alloys based on aluminum and magnesium comparatively recently. In this review, the application fields of metallic calcium and its influence on the structure and properties of various alloys are considered. Alloys based on aluminum–calcium eutectic have been systematically investigated over last few years, and it has been established that they possess casting properties no worse than these of silumins, and they can be hot-rolled and cold-rolled with a high degree of deformation. Ternary and more complex phase diagrams of systems including calcium are constructed and multicomponent alloys based on them are investigated. All these circumstances make it possible to outline several groups of new promising Ca-containing aluminum alloys: (i) alloys hardening without quenching due to the isolation of nanodimensional particles of Al₃Zr, Al₃Sc, and Al₃(Zr,Sc) phases; (ii) high-strength alloys alloyed with traditional hardening elements of the aluminum solid solution, such as zinc and magnesium; and (iii) composite alloys having more than 20% eutectic intermetallic compounds in the structure. All these materials have reduced density, an improved set of operational properties, increased corrosion resistance, and high manufacturability when producing cast and deformed half-finished products.     

Electrorefining zinc dross in ammoniacal ammonium chloride system

A zinc dross was cast into anodes and electrorefined in an ammoniacal ammonium chloride electrolyte (NH₃–NH₄Cl) to produce high purity zinc. The influence of several factors, such as zinc concentration, current density and temperature, on cathodic current efficiency and power consumption were investigated. The results indicated that increasing Zn concentration increased the current efficiency, but, very high Zn concentrations affected the progress of the electrolysis of zinc dross. The power consumption can be decreased effectively by increasing the temperature of electrolyte. High current density adversely affected the quality of the cathodes and increased the power consumption. The morphology of cathodic zinc can be improved by increasing Zn concentration at an appropriate current density and its purity was very acceptable. All the experimental results obtained showed a technical feasibility of the NH₃–NH₄Cl system as an electrolyte system for electrorefining of zinc dross.     

碳化沉淀法从中和渣浸出除杂液中分离回收锌和镁

基于碳酸锌和碳酸镁溶度积的差异,本文开展了碳化沉淀法分离回收锌、镁的研究,在理论计算的基础上,借助电感耦合等离子体发射光谱仪（ICP-OES）、X射线衍射仪（XRD）等表征手段,考察了碳酸盐种类及用量、温度等因素对锌、镁分离效果的影响规律,查明了中和渣浸出除杂液中锌、镁分离的调控方法。理论计算表明,以碳酸盐作为沉淀剂时,锌优先沉淀,且在镁离子沉淀之前,锌已沉淀完全。实验结果表明,相对Na₂CO₃、NaHCO₃、NH₄HCO₃等碳酸盐,以MgCO₃为沉淀剂进行镁、锌分离的效果更佳。实验所得的较优工艺条件为反应温度90 ℃,碳酸镁过量系数1.20,反应时间90 min,加料速度2.10 g/min。在该条件下,锌沉淀率达99.99%以上,镁沉淀率低于0.10%,实现了镁、锌的有效分离。所得沉锌渣为碱式碳酸锌,纯度较高,可达到工业碱式碳酸锌合格品（HG/T 2523—93）的技术指标。该方法简单易行,锌、镁分离效果好,且锌、镁均可资源化利用。      

Synthesis of the nitrides of Group II elements

Conclusions A study has been made, using kinetic, chemical, and x-ray diffraction methods, of the reactions of magnesium and zinc with ammonia. It has been established that the kinetics of magnesium and zinc nitride formation in ammonia is described by pseudotopokinetic equations. The reaction of magnesium takes place in the topokinetic range, with penetration into the diffusional range, while the reaction of zinc with ammonia is controlled by topochemical processes. In both cases surface activation is observed. The mechanism of formation of the nitrides of Group II elements is examined, ans suitable process parameters for the synthesis of the nitrides of Group II metals are indicated.Deceased.Translated from Poroshkovaya Metallurgiya, No. 2(206), pp. 57–62, February, 1980.     

Microstructural Evolution of the 55 Wt Pct Al-Zn Coating During Press Hardening

Press hardening is increasingly being used to produce ultra-high strength steel parts for passenger cars. Al-Si, Zn, and Zn-alloy coatings have been used to provide corrosion protection to press hardening steel grades. The use of coatings has drawbacks such as coating delamination or liquid metal-induced embrittlement. In the present work, the microstructural evolution of Al-Zn coating during press hardening was studied. The 55 wt pct Al-Zn coating can in principle provide both Al barrier protection and Zn cathodic protection to press hardened steel. During the heat treatment associated with the press hardening, the 55 wt pct Al-Zn alloy coating is converted to an intermetallic surface layer of Fe₂Al₅ and a FeAl intermetallic diffusion layer. The Zn is separated from both intermetallic compounds and accumulates at grain boundaries and at the surface. This Zn separation process is beneficial in terms of providing cathodic protection to Al-Zn coated press hardening steel.     

A unified theory for some effects of hydrogen source,alloying¦elements,and potential on crack growth in martensitic AISI 4340 steel

The effects of hydrogen on crack growth in martensitic AISI 4340 steel are shown to be fundamentally the same whether the hydrogen is supplied as molecular gas, through stress corrosion, or by electrolytic charging. At a given yield strength differences observed in the values of threshold stress intensity for crack growth are proposed to be linked to the degree of dissociation of the hydrogen near the crack tip, and hence to the concentration of hydrogen developed in the critical crack-tip region. Over a range of yield strength values, an upper bound of threshold stress intensity is developed in molecular hydrogen gas and a lower bound on exposure to atomic hydrogen from cathodic charging during or prior to testing. The open circuitK _Iscc values of the steel fall always within the upper and lower bounds, but the values ofK _Iscc may be moved to the lower bound by coupling to magnesium (cathodic charging) or to the upper bound by coupling to copper (anodic polarization). Variations in the concentration of carbon or manganese in the steel at a fixed yield strength produce effects on the value ofK _Iscc similar to the effects produced by cathodic or anodic polarization. With the lower concentrations of carbon or manganese the steel acts as if it were coupled to copper and at the higher concentrations as if coupled to magnesium. Carbon and manganese are therefore proposed to shift the positions of local anodes and cathodes and so influence the proportions of molecular and atomic hydrogen which reach the critical crack-tip region. The proposal is supported by data which show that only cathodic polarization affects the threshold stress intensity of the lowest carbon and manganese steelsK _Iscc is lowered) whereas only anodic polarization affects the higher carbon or manganese steels(K _Iscc is raised).     

Delamination Effect on Flutter of Homogeneous Laminated Plates

The effect of delamination on the flutter boundary of two‐dimensional laminated plates are investigated theoretically. Linear‐plate theory and qusai‐steady aerodynamic theory are employed. A simple beam‐plate‐theory model is developed to predict the flutter boundaries of delaminated homogeneous plates with simply supported ends. The effects of delamination position, size, and thickness on the flutter boundary are studied in detail. The results reveal that the presence of a delamination degraded the stiffness and the natural frequencies of the plate and thereby decreases the flutter boundary of the plate. However, for certain geometries the flutter boundaries were raised due to the flutter coalescence modes of the plate altered by the presence of a delamination in the plate.     

Effects of additives on zinc electrowinning from industrial waste products

An investigation of the effects of some additives on zinc electrowinning from a weak acidic sulphate electrolyte prepared from an industrial waste product has been carried out. Experiments were done in the presence of additives such as aluminium sulphate, animal glue and an extract of horse-chestnut nuts (HCE), used alone or in different mixtures.Using a rotating disc electrode (RDE) and cyclic voltammetry, the influence of the additives on the polarization curves and on the voltammograms was studied. SEM was used to determine the structure and the morphology of deposits.The results indicated that the additives tested exert a beneficial effect on the quality of the zinc deposits. They increase the cathodic polarization and promote levelling. Al₂(SO₄)₃ influences the reduction of zinc ions, increasing the nucleation overpotential and the deposition rate of zinc on the cathode. The conjoint use of Al₂(SO₄)₃, animal glue and HCE results in smooth, slightly bright deposits, showing a beneficial effect of the mixture on zinc electrodeposition. The analysis of deposit purity suggested that the additives inhibit the discharge rate of impurity metal ions, such as copper and lead, whose deposition is diffusion controlled.     

Fundamental studies on chlorine behavior as related to zinc electrowinning from aqueous chloride electrolytes

Measurements were made on the transport and equilibrium properties of dissolved chlorine in aqueous HC1, HCl-ZnCl₂, HCl-MgCl₂, and water. These measurements included solubility, absorption rates during bubbling, stripping rates during nitrogen bubbling, and cathodic reduction rates. The solubility of chlorine was found to be affected by speciation into aqueous Cl₂, HC1O, and C1₃ −. With increasing HCl concentration, the solubility of chlorine decreased to a minimum at 0.2 mol dm⁻³, followed by a slow and linear increase. Metal chloride salts depressed the chlorine solubility approximately in proportion to concentration. Mass transfer of aqueous chlorine was found to support a current of about 100 A m⁻² from a chlorine-saturated ZnCl₂-HCl solution under typical zinc electrowinning conditions. Comparisons with published zinc electrowinning papers indicate that air sparging would eliminate dissolved chlorine sufficiently to remove the need for diaphragm cell separation of dissolved chlorine, insofar as current inefficiencies due to cathodic chlorine reduction are concerned.     

Selective Oxidation and Surface Segregation in High Strength Steels during Short Term Annealing in H2‐N2 ‐ Influence of B on Surface Chemistry

In order to achieve appropriate mechanical properties, new high strength steels aimed for the car industry have to be alloyed with solution strengthening elements. The annealing treatment undergone on cold rolled sheets induces the selective oxidation of alloying elements such as Al, Mn, Si and Cr. The formed oxides exhibit a poor wetting by the Zn bath during hot dip galvanising, thus deteriorating the properties of the zinc coating. While surface‐segregating elements get oxidised, they interact with each other through the formation of spinels and/or mixed oxides during annealing and oxides which have a deleterious effect on wetting can be formed. The formation of (Mn, B) oxide was observed on alloys containing even very small amounts of B and this oxide is almost not wetted at all by Zn. Boron is added to interstitial‐free steels to improve the cold work embrittlement, by replacing phosphorus at the grain boundaries. In this paper, the selective oxidation of steels with and without B, in 5 vol. % H₂‐N₂ atmosphere at 820°C and different dew points was investigated. We found a very strong effect of segregation and oxidation of B on Si and S segregation and oxidation behaviour.     

The Manufacture and Characterisation of Reinforced Magnesium Foams

In the project introduced here, the manufacture of light‐metal foams based on magnesium are investigated and enhanced. Such foams possess an excellent mass‐volume ratio and are therefore perfectly suited as light and effective reinforcing elements. Apart from other functional properties, their suitability as energy absorbing crash elements is to be particularly emphasised and is the focus of the investigations here. In the case of impact loading, the energy is largely transformed into the work of plastic deformation during a reduction in volume. Although metallic foams themselves possess only low absolute strengths, it is expedient to employ them in the form of material combinations like sandwich structures or composites by integrating additional internal reinforcing elements. The latter approach is pursued in the present project. Both the initial results of the feasibility study and also the metallographic and mechanical investigations for characterising reinforced magnesium foams are presented.     

Effects of zinc coatings on the stress corrosion cracking and hydrogen embrittlement of low-alloy steel

The effects of electroplated and hot-dip zinc coatings on the fracture of low-alloy steel AISI 4140 bars tempered to hardnesses in the range Rc 33 to 49 were studied. Either electroplated or hot-dip zinc coatings decrease resistance to stress corrosion cracking,i.e., they reduceK _sc, the threshold stress intensity for stress corrosion cracking in 3.5 wt pct NaCl solution. AboveK _scelectroplated-zinc coatings do not appear to affect the crack-growth rate, although the incubation period prior to the onset of crack growth is reduced. Hot-dip zinc coatings increase stress corrosion crack growth rates slightly because of the additive effect of internal dissolved hydrogen. Hot-dip zinc coatings reduce the critical stress intensity for fracture in the absence of a corrosive environment because of embrittlement by internal hydrogen which is released from traps during hot-dip coating and confined by the inter metallic coatings which form on the steel surface in the hot dip bath. A simple fracture mechanics analysis indicates that either increasing diameter or the presence of a zinc coating lowers the critical hardness at which the stress corrosion cracking of structural bolts can occur.