Cell/dendrite transition and electrochemical corrosion of Pb-Sb alloys for lead-acid battery applications

The aim of this article is focused on a comparative experimental study of the electrochemical feature of as-cast Pb-2.2 wt.% Sb alloy with cellular/dendritic transition for applications in the manufacturing of lead-acid battery parts. A water-cooled unidirectional solidification system is used to obtain the alloy samples. Electrochemical impedance spectroscopy (EIS) plots, potentiodynamic polarization curves and equivalent circuit analysis are used to evaluate corrosion resistance in a 0.5 M H₂SO₄ solution at 25 °C. The cellular Pb-2.2 wt.% Sb alloy is found to have a current density which is of about 3 times lower than that of the dendritic Pb-2.2 wt.% Sb alloy. The Pb-2.2 wt.% Sb alloy has lower current density than both the Pb-1 wt.% Sb and the Pb-6.6 wt.% Sb alloys evidencing its potential for application as positive grid material in lead-acid batteries. It is also verified that a conventional casting with low cooling rate of about 0.6 °C s⁻¹ produces coarser cellular spacings which is more appropriate for the manufacturing of the Pb-2.2 wt.% Sb alloys grids due to its corresponding electrochemical behavior.     

Comparison of electrochemical performance of as-cast Pb-1 wt.% Sn and Pb-1 wt.% Sb alloys for lead-acid battery components

A comparative experimental study of the electrochemical features of as-cast Pb-1 wt.% Sn and Pb-1 wt.% Sb alloys is carried out with a view to applications in the manufacture of lead-acid battery components. The as-cast samples are obtained using a water-cooled unidirectional solidification system. Pb-Sn and Pb-Sb alloy samples having similar coarse cell arrays are subjected to corrosion tests in order to assess the effect of Sn or Sb segregation in the cell boundary on the electrochemical performance. Electrochemical impedance spectroscopy (EIS) diagrams, potentiodynamic polarization curves and an equivalent circuit analysis are used to evaluate the electrochemical parameters in a 0.5 M H₂SO₄ solution at 25 °C. Both the experimental and simulated EIS parameters evidence different kinetics of corrosion. The Pb-1 wt.% Sn alloy is found to have a current density which is of about three times lower than that of the Pb-1 wt.% Sb alloy which indicates that dilute Pb-Sn alloys have higher potential for application as positive grid material in maintenance-free Pb-acid batteries.     

Influence of bismuth on the age-hardening and corrosion behaviour of low-antimony lead alloys in lead/acid battery systems

The effects of bismuth additions in the range 0.006–0.086 wt.% on the metallurgical and electrochemical properties of Pb-1.5 wt.% Sb alloy are investigated. The self-discharge behaviour of batteries produced with grids of the doped alloys is also evaluated. Addition of bismuth is found to exert no significant effects on the age-hardening behaviour, general microstructure or grain size of the alloy. It does, however, influence the morphology of the eutectic in the inter-dendritic regions. The latter changes from a mainly lamellar to an irregular type with increasing bismuth content. The corrosion rate of the grid decreases with increase of the bismuth content. Attack occurs preferentially in the inter-dendritic regions where there is an enrichment of both antimony and bismuth. Electron-probe microanalysis shows that the corrosion zone consists of a tri-layered structure, namely: a dense, continuous, inner layer (PbO_1.1); a central layer (PbO_1.8·PbSO₄); a porous outer layer n(PbO_1.8)·PbSO₄, with n=2–8. In the latter, the value of n increases in the direction of corrosive penetration into the grid. Data from atomic absorption spectrometric analysis reveal that bismuth, after oxidative leaching from the grid substrate, is retained mainly in the corrosion layer. A key observation is that bismuth (i.e., up to ∼0.09 wt.%) does not affect the self-discharge behaviour of batteries.     

The interrelation between mechanical properties, corrosion resistance and microstructure of Pb-Sn casting alloys for lead-acid battery components

It is well known that there is a strong influence of thermal processing variables on the solidification structure and as a direct consequence on the casting final properties. The morphological microstructural parameters such as grain size and cellular or dendritic spacings will depend on the heat transfer conditions imposed by the metal/mould system. There is a need to improve the understanding of the interrelation between the microstructure, mechanical properties and corrosion resistance of dilute Pb-Sn casting alloys which are widely used in the manufacture of battery components. The present study has established correlations between cellular microstructure, ultimate tensile strength and corrosion resistance of Pb-1 wt% Sn and Pb-2.5 wt% Sn alloys by providing a combined plot of these properties as a function of cell spacing. It was found that a compromise between good corrosion resistance and good mechanical properties can be attained by choosing an appropriate cell spacing range.     

Microstructure and electrochemical corrosion behavior of a Pb-1 wt%Sn alloy for lead-acid battery components

The aim of this study was to evaluate the effect of solidification cooling rates on the as-cast microstructural morphologies of a Pb-1 wt%Sn alloy, and to correlate the resulting microstructure with the corresponding electrochemical corrosion resistance in a 0.5 M H₂SO₄ solution at 25 °C. Cylindrical low-carbon steel and insulating molds were employed permitting the two extremes of a significant range of solidification cooling rates to be experimentally examined. Electrochemical impedance spectroscopy (EIS) diagrams, potentiodynamic polarization curves and an equivalent circuit analysis were used to evaluate the electrochemical corrosion response of Pb-1 wt%Sn alloy samples. It was found that lower cooling rates are associated with coarse cellular arrays which result in better corrosion resistance than fine cells which are related to high cooling rates. The experimental results have shown that that the pre-programming of microstructure cell size of Pb-Sn alloys can be used as an alternative way to produce as-cast components of lead-acid batteries with higher corrosion resistance.     

Tracing the influence of small additions of antimony to zinc on the hydrogen evolution and anodic dissolution processes of zinc as anodes for alkaline batteries application

The processes of hydrogen evolution reaction and anodic dissolution of zinc and zinc-antimony alloys with different antimony amounts (0.5 and 1%) immersed in 6 M KOH were tested via many electrochemical methods as Tafel polarization, cyclic voltammetry (CV), impedance spectroscopy (EIS), and charge-discharge. Newly formed phases, the morphology of the surface, and chemical composition for Zn and Zn–Sb alloys after and before corrosion were determined via appreciated analysis instruments as X-ray diffraction (XRD), scanning electron microscopy (SEM) provided with an energy-dispersive X-ray spectroscopy detector (EDS). The results of Tafel plots exhibited that, the protection efficiency of corrosion (η%) gets greater with the increase of both temperature and Sb content. It is impressive to note that, η% for Zn–Sb alloy (1%Sb) reaches the highest value of 98.55% at the higher studied temperature (55 °C). The potential of corrosion (E_corr.) is shifted to a more negative position with the increase of antimony addition to zinc. This reveals that minor alloying amounts of Sb with Zn plays an important role to improve the suppression of the evolved hydrogen, charge efficiency, capacitance, and lifetime of alkaline batteries. Surface investigations revealed the presence of ZnSb and Zn₄Sb₃ phases on the alloy surface have an essential function in the protection of zinc anodes, and improvement of charge-discharge.     

Comparison of novel composite anodes with different proportions of α/β-PbO2 and the application in long-period zinc electrowinning

Zinc is an important non-ferrous metal material, of which the hydrometallurgy process has requirements for anode materials. In the present work, Pb-0.6%Sb/α-PbO₂/β-PbO₂-MnO₂(CNTs) composite electrodes with different proportions of α/β-PbO₂ were obtained and compared before and after zinc electrolytic simulation process. The optimal one was contrasted with traditional Pb-0.8 wt%Ag anode in long-period zinc electrowinning application. It was found that α-PbO₂ transition layer could effectively improve the electrodeposition distortion of β-PbO₂ surface and make the corrosion resistance better. Novel composite anode with more β-PbO₂ proportion showed weaker internal resistance and greater OER electrocatalytic activity. The anode obtained by controlling the electrodeposition time of α&β-PbO₂ phases at 1.5 h & 1 h had the best physical and chemical properties. Its cell voltage value (2.833 V) was 299 mV lower than that of traditional Pb-0.8 wt%Ag anode (3.132 V) in zinc electrodeposition. In addition, the compactness of the composite anode was improved under the function of active particles. The energy-saving effect of novel composite anode in long-period zinc electrowinning application was obvious.     

Wrought lead-calcium-tin alloys for tubular lead/acid battery grids

Lead/acid batteries with tubular grids for the positive electrodes give flatter discharge curves and higher cycle life than batteries using flat plates. Most tubular grids for motive-power batteries contain 9–11 wt.% antimony. Recently, alloys with 1–6 wt.% antimony have been used for reduced maintenance batteries. Sealed, valve-regulated batteries with tubular positive grids for motive power, telecommunications, and UPS service are produced from cast lead-calcium-tin alloys. While these alloys permit the construction of such batteries, cast PbCaSn alloys are significantly inferior to cast PbSb alloys in mechanical properties. Wrought PbCaSn alloys, when used for tubular grids, permit the application of maintenance-free alloys with mechanical properties comparable with, or higher than, those of high-antimony alloys. Wrought materials increase life due to the absence of casting defects. Wrought lead-calcium alloys also offer a dramatic improvement in creep and corrosion resistance compared with conventional cast, tubular, PbCaSn alloys, as well as superior conductivity to cast PbSb. Wrought PbCaSn alloys permit the production of tubular grids at high speed in shapes and forms that are difficult to produce from cast materials. These grid shapes can lead to higher performance, higher discharge-rate, tubular plates. This paper discusses the mechanical properties, grain structure, and corrosion behaviour of cast and wrought PbCaSn and PbSb alloys for tubular grids. It also suggests manufacturing techniques for high performance, wrought, tubular plates.     

Electrochemical characteristics of binary silver alloys in alkaline solution

The electrochemical features, electrode capacity and corrosion stability, of silver alloys with Tl, Pb, P, Sb, Ge and In have been investigated. Compared to silver some silver alloys showed improved silver oxide formation and conductivity. The best effects, i.e., dramatic increases of 150% for formation of oxide, were obtained with small amounts of alloying component: 0.44% Tl or 0.44% Pb. Based on obtained results, those effects could be explained in terms of increase of real electrode surface as a consequence of ingredients oxidation, preceding the silver oxidation.     

Role of minor alloying elements on the performance of lead/acid battery grids. Part 2. Corrosion of lead-arsenic alloys

Corrosion of PbAs alloys (As = 0.1, 0.2, 0.3 and 0.4%) in 5.0 M H₂SO₄ solutions at 30°C was studied under open-circuit, potentiostatic and galvanostatic polarization conditions. The sulfation process under open-circuit conditions increased as the As concentration increased and the open-circuit potential shifted to more cathodic values. The presence of As affected significantly the potentiostatic polarization curve and caused a substantial decrease in passivity current and increased the overpotentials of both the O₂- and the H₂-evolution reactions. The self-discharging process decreased as the concentration of As increased with formation of substantial amounts of lead oxide beside PbSO₄. When PbAs alloys were subjected to alternative cathodic and anodic galvanostatic polarization cycles, the corrodable layer thickness increased in the order of: Pb-0.1%As>Pb-0.3%As%>Pb-0.4%As>Pb>Pb-0.2%As. The efficiency of PbO₂ formation also depended on the percentage As.     

In situ EC-AFM observation of antimony effect for lead dioxide electrode

The surface morphologies of lead dioxide layers, which were formed on a pure lead substrate and the Pb–Sb a (100 ppm–3%) alloy substrate, were directly observed with the electrochemical atomic force microscope (EC-AFM) in 1.250 g/cm³ sulfuric acid electrolyte and then they were analyzed with X-ray diffraction (XRD). The particle size of the lead dioxide became significantly smaller with the increase of the amount of antimony in the substrate alloy. From this result, it was considered that such small particle size serves to increase the reaction area of the positive electrode and the total electrical contact area between the positive active material (PAM) particles. Also, the interface resistance between grid and the PAM can become lower, if the density of the corrosion layer formed around the grid were to be higher for the small particles. By XRD analysis, it was found that the inter-atomic distance of the lead dioxide on the Pb–3 wt.% Sb alloy substrate shrank compared to that on a pure Pb substrate.     

The effect of the change in the amount of Sb doping in ZnO nanorods for hydrogen gas sensors

In this study, pure and variable content Sb doped ZnO nanorods (NRs) were grown by a simple spray pyrolysis method successfully. Structural analysis has showed that all the films are indicating preferential dominant c-axis (002) plane from x-ray diffraction (XRD) measurements. It is observed that Sb doping does not result in changes in lattice parameter indicating no lattice distortion. Raman measurements has indicated Sb doping related modes in ZnO NRs especially defect related. SEM images has shown uniform hexagonal close packing NR structures uniformly distributed throughout the film. X-ray photoelectron spectroscopy (XPS) has displayed lower incorporation of the Sb from the precursor to the Sb doped NRs. Hydrogen gas sensor performances of these NRs has investigated. 5.0 wt% Sb doped ZnO NR sample has showed outstanding response with 23-fold response to 10 ppm hydrogen gas level at 250 °C.     

The roles of cellular and dendritic microstructural morphologies on the corrosion resistance of Pb–Sb alloys for lead acid battery grids

During the past 20 years, lead acid batteries manufacturers have modified grid manufacturing processes and the chemical composition of the used alloys in order to decrease battery grid weight as well as to reduce the production costs, and to increase the battery life-time cycle and the corrosion resistance. The aim of this study was to evaluate the effects of cellular and dendritic microstructures of two different Pb–Sb alloys on the resultant corrosion behavior. A water-cooled unidirectional solidification system was used to obtain cellular and dendritic structures. Macrostructural and microstructural aspects along the casting have been characterized by optical microscopy and SEM techniques. Electrochemical impedance spectroscopy and potentiodynamic polarization curves were used to analyze the corrosion resistance of samples in a 0.5 M H₂SO₄ solution at 25 °C. For cellular microstructures the corrosion rate decreases with increasing cell spacing. In contrast, finer dendritic spacings exhibit better corrosion resistance than coarser ones. The microstructural pre-programming may be used as an alternative way to produce Pb alloy components in conventional casting, rolled-expanded, and continuous drum casting with better corrosion resistance.     

Corrosive characteristics of bioethanol and gasoline blends for metals

Corrosive characteristics of lignocellulosic bioethanol on metals, such as mild steel, copper, and aluminum were studied by static immersion test at room temperature. Effect of metals on degradation of fuel properties, such as pHe, total acid number, acidity, density, viscosity, calorific value, flash point, and color changes were evaluated. Moreover, the transformation of water content and oxidation products in the fuel were investigated. Effect of fuel blends on corrosion rate, chemical structure of metals, and morphology of corrosion product were also examined. Results showed that the corrosion of metals in E50 (50% bioethanol and 50% gasoline) is high compared with E25 and E0. Moreover, degradation of fuel properties and compositional changes in E25 and E50 were high compared with E0. The corrosion rate of aluminum in E50 (0.216 mpy) was lower than copper (0.441 mpy) and mild steel (0.487 mpy). Moreover, the corrosion rate of aluminum in E25 (0.096 mpy) was also lower than copper (0.285 mpy) and mild steel (0.297 mpy). It was discovered that corrosion of materials and degradation of fuel properties were 2.4 times high in higher ethanol blends (above E25) compared with lower ethanol blends (up to E25). Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of cell size and macrosegregation on the corrosion behavior of a dilute Pb–Sb alloy

The aim of this study was to examine the effect of cooling rate on the cellular growth of a Pb–0.85 wt%Sb alloy and to evaluate the influences of cell size and of the corresponding macrosegregation profile on the resultant corrosion behavior. In order to obtain the as-cast samples a water-cooled unidirectional solidification system was used. Such experimental set-up has permitted the development of a clear cellular structural array even for relative high cooling rates and has allowed a wide range of solidification conditions to be analyzed. Macrostructural and microstructural aspects along the casting were characterized by optical microscopy and scanning electron microscope (SEM) techniques. The electrochemical impedance spectroscopy technique and potentiodynamic curves (Tafel extrapolation) were used to analyze the corrosion resistance of samples collected along the casting length and immersed in a 0.5 M H₂SO₄ solution at 25 °C. It was found that the corrosion rate decreases with increasing cell spacing and that the pre-programming of microstructure cell size can be used as an alternative way to produce as-cast components of Pb–Sb alloys, such as battery grids, with better corrosion resistance.     

The effect of method of preparation on the corrosion resistance and catalytic activity during corrosion of tungsten carbide II. Changes in the catalytic activity of tungsten carbides during the corrosion process

Sedimented electrodes were used for the investigation of the changes in the catalytic activity during corrosion in 4.5 and 9.9N H₂SO₄ of tungsten carbides synthesized under different conditions. It is shown that during corrosion the specific activity of all the samples studied reaches a maximum after a certain exposure time. The same phenomenon is observed also during the periodic contact of the corroding samples with hydrogen. The catalytic activity decreases with increase in the quantity of tungsten oxides formed during corrosion. In 4.5N H₂SO₄ the specific activity of the tested samples is subjected to more pronounced changes. Corrosion processes lead to some exceptions in the general rule that carbides synthesized from WO₃ display a higher specific activity than those synthesized from H₂WO₄ (w).     

Effect of antimony on the anodic corrosion of lead and oxygen evolution at the Pb/PbO2/H2O/O2/H2SO4 electrode system

When a Pb electrode immersed in H₂SO₄ solution is polarized in the PbO₂ potential range the following electrode system is formed: Pb/PbO₂/H₂O/O₂/H₂SO₄. At the oxide/solution interface oxygen evolution takes place. The semiproducts of this reaction, O atoms and O⁻ radicals, diffuse into the anodic layer and oxidize the metal. As a result of a solid-phase reaction the metal is oxidized first to tet-PbO and then further oxidized to PbO₂. By examining the changes in the Tafel slopes of the above reactions and by analyzing the chemical composition of the anodic layer, the effect of Sb on the above processes is assessed.Antimony was introduced into the electrode system either by alloying it with the metal or by adding it to the H₂SO₄ solution. It was established that Sb lowers the oxygen overvoltage and increases the rate of anodic corrosion of lead irrespective of the way in which it was introduced into the system. Antimony increases the stoichiometric coefficient of the oxide layer, hence, it enhances the oxidation of PbO to PbO₂. The results of these investigations confirm the mechanism of the processes proceeding during anodic oxidation of lead.     

Transport properties of some bismuth-antimony alloys

The thermal and electrical conductivities, as well as the thermoelectric powers for single crystals of BiSb alloys, in the temperature range 60 to 90 K have been measured. The thermoelectric power behaviour is attributed to a change from extrinsic to intrinsic conduction occurring near 80 K for alloys with between 9 and 32 atomic % Sb. For alloys having less than 24 atomic % Sb, the phonons suffer a large strain field scattering whereas, for higher concentrations, bipolar diffusion probably ensues.     

A facile control in free-carbon domain with divinylbenzene for the high-rate-performing Sb/SiOC composite anode material in sodium-ion batteries

Sodium-ion batteries (SIBs) are not only cheaper to produce than lithium-ion batteries, but the reserves of sodium in the world are also more uniform and abundant. Thus, efforts are being made to utilize sodium-ion batteries as next-generation large-capacity energy-storage devices. Sb-based anode materials have emerged as a popular alloying material for SIB owing to their high theoretical capacity. However, Sb exhibits the problem of capacity fading owing to excessive volume expansion (approximately 390%). SiOC is a buffer material that has been investigated in terms of its ability to overcome these disadvantages; however, SiOC has the disadvantage of containing a fixed and limited free-carbon domain. Here, high free-carbon contained in Sb/SiOC composites (HFC-Sb/SiOC) was easily synthesized by the heat treatment of divinylbenzene (DVB), a liquid carbon source, with silicone oil and Sb acetate. Sb nanoparticles were uniformly embedded in DVB-modified SiOC with increased free-carbon domains. This composite material showed cycling stability (344.5 mAh g⁻¹ after the 150 cycles at 0.2 C) and outstanding rate properties (197.5 mAh g⁻¹ at 5 C) as the SIB anode. The enhanced electrochemical performance is result from the increased free-carbon domains in the SiOC matrix caused by the addition of DVB, which makes the characteristics of the SiOC material softer and more elastic, suppressing volume changes and enhancing the electrical conductivity.     

新老混凝土中钢筋通电加速锈蚀特性试验研究

为研究新老混凝土中抗剪钢筋锈蚀的相关特性,采用通电加速锈蚀方法分析了设计锈蚀率分别为5%、10%条件下新老混凝土中抗剪钢筋的锈蚀特性,探究了不同位置处钢筋锈蚀的异同。结果表明,混凝土浇筑面锈蚀率大于非浇筑面;钢筋锈蚀率和锈蚀效率与混凝土强度呈正相关关系;设计锈蚀率10%较5%的锈蚀效果更好;新老混凝土结合面处钢筋锈蚀情况较其他地方严重。