Investigation on characteristics of anodic film formed on PbCaSnCe alloy in sulfuric acid solution

The electrochemical properties of the anodic films formed on PbCaSnCe and PbCaSn alloys at 0.9 V (versus Hg/Hg₂SO₄ electrode) in 4.5 mol/L sulfuric acid solution were investigated by linear sweeping voltammetry (LSV), ac voltammetry (ACV), electrochemical spectroscopy impedance (EIS), capacitance measurement and X-ray photoelectron spectroscopy (XPS) technology. Based on Mott-Schottky analysis, the effect of cerium on the semiconductor properties of anodic film is discussed as well in this paper. The experimental data shows that cerium can significantly decrease the impedance of the anodic film on PbCaSn alloy, and can improve the corrosion resistance of the alloy. It can be inferred from the capacitance measurement result that the passive film should be an n-type semiconductor. The addition of cerium can decrease the slope of M-S plot, which indicates the increasing of defect density in the film, and this can contribute to improve the conductivity of the anodic film on PbCaSn alloy. XPS results shows that the anodic film formed on PbCaSnCe alloy is consisted of PbO_1+x (0 < x < 1) and PbSO₄, while for the anodic film formed on PbCaSn alloy, PbO and PbSO₄ are the major component. Considering the better conductivity of PbO_1+x (0 < x < 1) than that of PbO, it is concluded that PbCaSnCe may serve as the candidate of the new grid material for maintenance-free lead acid battery.     

The composition of the surface passive film formed on CoCrMo alloy in simulated physiological solution

The passive oxide films formed by electrochemical oxidation on CoCrMo alloy (ASTM F75) in simulated physiological solution were studied using X-ray photoelectron spectroscopy (XPS). The oxidation was performed in a closed system without exposure to laboratory air. The fitting procedure used allowed the separation of the measured spectra, Co 2p, Cr 2p, Mo 3d and O 1s, into contributions of various species. Quantitative evaluation included the determination of the composition, cationic fraction and thickness of the oxide layer formed. An insight into the structure of the layer was offered by angle-resolved XPS measurements. The addition of complexing agent, in the form of Na-citrate, to the physiological solution affects the passivation of CoCrMo alloy.     

The anodic polarization behavior of amorphous PdTiP alloys in NaCl solutions

The corrosion resistance and electrocatalytic activity for chlorine evolution of amorphous PdTiPalloys in NaCl solutions was investigated. Particular attention was given to the difference between amorphous and crystalline states and the effect of titanium addition. The corrosion rate of the amorphous alloys in the potential region for gas evolution was significantly lower than that of palladium over wide ranges of polarization potential and pH of solutions. This fact was attributed to the formation of a uniform passive film on the amorphous alloys and to the stabilization of passivity by the addition of titanium. The catalytic activity of the amorphous alloys for gas evolution was lower than that of palladium and decreased with an increase in titanium conten-t. The oxygen overvoltage of amorphous PdTiP alloys is considerably higher similarly to that of palladium     

The anodic oxide film on iron in neutral solution

The composition of the anodic passive oxide film on iron in neutral solution has been investigated by cathodic reduction, chemical analysis and ellipsometry. The cathodic reduction using a borate solution of pH 6·35 containing arsenic trioxide as inhibitor estimates iron in the film to be all iron (III), indicating that no magnetite layer is present. Oxygen in the film is estimated from the ellipsometric thickness to be in excess of the stoichiometric ferric oxide, suggesting the presence of bound water. The average composition is represented as Fe₂O₃.0·4H₂O, in which hydrogen may be replaced partly with iron-ion vacancy. The anodic oxide film is composed of an inner anhydrous ferric oxide layer, which thickens with the potential and an outer layer of hydrous ferric oxide whose thickness depends on the condition of passivation and environment.     

The anodic polarization characteristics of the graphite in alkaline solution

The anodic behaviour of a graphite electrode in alkaline solution was studied by means of the linear potential sweep method, the controlled potential electrolysis and the colourimetry. Linear sweep polarization curves indicated that the surface of graphite electrode is oxidized in the anodic region from ?0.3V.The numbers of electron participating in the oxidation of a carbon atom was calculated to be 1, 2, and 2 at 0.2, 0.3, and 0.4V, respectively, based on the quantity of electricity which was measured by the controlled potential electrolysis and the numbers of carbon atom on the surface of the graphite electrode, which was calculated with the double layer capacity.The structure of oxide layer formed on the graphite electrode was examined by the colourimetry with HgBr₂ and NaOEt. It was found that the oxide layer on the electrode contained carbonyl groups.     

Cathodic breakdown of anodic oxide film on Al and Al–Sn alloys in NaCl solution

The effect of cathodic polarisation on stability of defined oxide films on Al and Al–Sn alloys (with up to 0.40% Sn) has been investigated in a 0.5 M NaCl solution using the potentiostatic pulse method. The dependence of the cathodic current on time (in the period of 1, 10 and 100 s) was recorded on Al and Al–Sn alloys when subjected to a potential pulse from E_OCP to different negative values (up to −2.0 V). Anodic current responses to the return to the E_OCP were also recorded at three different time scales (1, 10 and 100 s). It has been established that the cathodic polarisation of passivated Al and Al–Sn alloys in a chloride solution is characterized by two regions of potentials with distinctly different phenomena: the range of low and high cathodic potentials (LCP and HCP). In the LCP range, the oxide film retains its properties, while in the HCP range cathodic breakdown and hydration of the oxide take place. The boundary between these two potential ranges shifts towards more negative potential values when the percentage of Sn in the alloy increases. The longer the duration of the cathodic pulse, the more positive the potentials at which the oxide film breakdown takes place. This shift is more marked with alloys containing higher percentage of Sn. Cathodic polarisation (duration of 100 s) activates alloys with 0.20% and 0.40% Sn for anodic dissolution.     

铝合金硫酸阳极氧化膜层颜色的形成与控制

给出了铝合金化学除油及硫酸阳极氧化工艺条件.分析了影响铝合金硫酸阳极氧化膜层颜色的因素,如铝合金成分,机械加工方式,膜层均匀度和腐蚀等.     

Hydrated structures in the anodic layer formed on lead electrodes in H2SO4 solution

SEM and TEM observations of the corrosion layer obtained during the potentiostatic oxidation of lead electrodes in H₂SO₄ solution have shown that, at potentials above 1.00 V vs Hg/Hg₂SO₄, a lead dioxide layer is formed with crystal and gel-like (hydrated) structures. The crystal zones of the corrosion layer contain - and -PbO₂ crystals. Applying controlled thermal degradation it has been established that hydrated zones (denoted as PbO(OH)₂) comprise about 10% of the corrosion layer. For comparison, the lead dioxide active mass of the lead-acid battery is hydrated over 30%. On prolonged polarization of the lead dioxide electrode at 1.50 V, the basic electrochemical reaction that takes place is oxygen evolution. It has been suggested that this reaction occurs mainly at the interface crystal/gel-like zones. On opening the circuit, the electrode potential reaches the equilibrium potential for the PbO₂/PbSO₄ system within a rather long period. This potential decay is related to the diffusion of oxygen through the bulk of the corrosion layer (probably through its hydrated zones) to the solution and to the metal. A suggestion is made that hydrated zones are also involved in the oxygen reaction.     

铝合金阳极氧化膜的性能研究

在硫酸电解液中加入适量由羧酸和有机化合物组成的添加剂,制得铝合金阳极氧化膜。研究了温度对所得氧化膜厚度和硬度和影响,并利用扫描电镜观察了氧化膜的结构。结果表明,高温下形成的氧化膜结构松散,厚度和硬度低,而加入添加剂后,氧化膜溶解减慢,在高温下所形成的氧化膜的厚度和硬度大大增加。     

Electron transfer across anodic films formed on tin in carbonate-bicarbonate buffer solution

Impedance and steady-state data were recorded in order to study the kinetics of electron transfer between passive tin electrodes and an electrolytic solution containing the K₃Fe(CN)₆-K₄Fe(CN)₆ redox couple. Film thickness plays a key role in determining the type of electronic conduction of these oxide covered electrodes. Electron exchange with the oxide takes place with participation of the conduction band in the semiconducting film. A mechanism involving direct electron tunneling through the space charge barrier is the most suitable to interpret the experimental evidence.     

Kinetics of anodic oxide film growth on indium in alkaline solution

Data are presented which describe the kinetics of repassivation of freshly generated indium surfaces of pH 14. The process is controlled by ion conduction through the growing oxide film under high electric field. The associated kinetic parameters are tabulated. At high potentials an excess anodic charge is observed; it is attributed to conversion of some of the barrier film into an non-barrier layer. Some kinetic data associated with this process are presented.     

Effect of grain orientation on the morphology, dielectric breakdown and optical behaviour of anodic film formed on Al–2wt%Cu binary alloy

Barrier-type anodic film growth on an Al–2wt%Cu alloy is shown to be dependent upon the crystallographic orientation of the substrate grains. Generally, on grains of orientations near [1 0 0], featureless amorphous films, with parallel film/electrolyte and alloy/film interfaces, are formed. Conversely, on grains of orientations near [1 1 0] and [1 1 1], anodic films with occluded oxygen-filled voids of different shape, size and population density, and with undulating film/electrolyte and alloy/film interfaces, are generated. It is also revealed that the population density of dielectric breakdown craters of the anodic film is dependent on the crystallographic orientation of substrate grains. Further, the anodized Al–Cu alloy shows a grain orientation dependent coloured appearance. The colouring arises from interference and unbalanced reflection of certain wavelengths of light caused by the thin anodic films of different morphologies.     

烧结型白铜多孔管在NaCl溶液中的结垢性能

采用电加热的方式,研究了换热器用烧结型多孔管与光滑铜管在NaCl溶液中的结垢性能,对污垢热阻随测量时间、溶液浓度等的变化而产生的变化进行了分析,并与机加工多孔管的数据进行了比较.实验结果表明,烧结型多孔管与普通光滑管相比确实有抗垢性能,同时为此种产品应用于海水淡化的多效蒸发装置提供了实验数据.     

Surface analyses of anodic oxides films formed on Fe-3% Ti alloy

Surface analyses of the anodic oxide films formed on Fe—3% Ti alloy in deaerated pH 3.0 phosphate solution were performed with Auger electron spectroscopy (AES) and ellipsometry to evaluate the role of allying titanium in the corrosion resistance of iron.The 3%-addition of titanium reduced significantly the passivity-maintaining current density of iron as well as the maximum-active current density. Auger analysis revealed that titanium was enriched markedly in the anodic oxide films formed on Fe—3% Ti alloy and that a significant amount of phosphorus was distributed in the whole range of film thickness. Both the amount of titanium enriched in the film and the film thickness (20–40 nm) ellipsometrically obtained were proportional to the amount of electric charge required for passivation. Atomic absorption analysis of the solution indicated that the formation of a titanium-enriched film resulted from a preferential dissolution of iron as ferrous ions.From the measurement of the potential decay curves of the Fe—3% Ti alloy and pure iron electrodes passivated for different hours, it was concluded that the titanium-enriched layer promoted the passivity by suppressing, though incompletely, the active dissolution, whereas the substantial passivity of the alloy was attributed to the iron oxide film of barrier type formed at the interface of titanium-enriched layer/alloy substrate.     

Electrochemical and structural characterization of AZ63 alloy surface film in MgSO4 solution

The formation and growth of surface film on AZ63 (Mg–6Al–3Zn) magnesium alloys were studied in 2 M MgSO₄ aqueous solution using electrochemical methods. Surface examinations were carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and microscopic Fourier transform infrared spectroscopy. Experimental results show that the corrosion current decreases with prolonged immersion time, the three stages of hydrogen evolution rate correspond with the growth processes of the surface film on AZ63 magnesium alloys, and charge transfer resistance increases with the accumulation of corrosion products. A layer of MgO with sulfate salt grains underneath seems smooth at first. However, a few surface micro-cracks caused by inner stress appear on the smooth base film after 5 h of immersion, followed by the aggregation of spherical grains and the formation of cracks after 12 h. It is suggested that sulfate salt, carbonate salt, and hydroxide of magnesium should be the main composition of the surface film.     

铝阳极氧化膜层着色故障处理

对铝及其合金阳极氧化膜层常见的着色故障进行了总结:膜层不着色,局部不着色,颜色浅而易褪,着色膜上出现白点,着色膜发花或黯淡以及着色不牢固等。分析了产生各种故障的原因。提出了故障排除方法。     

6063铝合金在碱性含氧酸盐溶液中的高压阳极氧化

为比较在高压阳极氧化条件下不同电解液体系中碱性含氧酸盐对6063铝合阳极氧化膜层厚度及氧化时间的影响,将6063铝合金置于Na2SiO3、Na2HPO4和NaAlO2三种电解液体系中制备出阳极氧化膜。用涡流测厚仪测试了膜层厚度,通过点滴腐蚀实验评价了Na2SiO3体系所得氧化膜的耐腐蚀性能,利用扫描电子显微镜(SEM)观察分析了氧化膜的表面形貌。结果表明,钨酸钠能显著提高膜层厚度和膜层的耐腐蚀性能,六偏磷酸钠(SHMP)能延长氧化时间,提高膜层的硬度;在硅酸盐体系中钨酸钠和六偏磷酸钠按1∶1的比例加入,能得到致密的高耐蚀性阳极氧化膜层。     

6063铝合金在碱性含氧酸盐溶液中的高压阳极氧化

为比较在高压阳极氧化条件下不同电解液体系中碱性含氧酸盐对6063铝合阳极氧化膜层厚度及氧化时间的影响,将6063铝合金置于Na2SiO3、Na2HPO4和NaAlO2三种电解液体系中制备出阳极氧化膜.用涡流测厚仪测试了膜层厚度,通过点滴腐蚀实验评价了Na2SiO3体系所得氧化膜的耐腐蚀性能,利用扫描电子显微镜(SEM)观察分析了氧化膜的表面形貌.结果表明,钨酸钠能显著提高膜层厚度和膜层的耐腐蚀性能,六偏磷酸钠(SHMP)能延长氧化时间,提高膜层的硬度;在硅酸盐体系中钨酸钠和六偏磷酸钠按1:1的比例加入,能得到致密的高耐蚀性阳极氧化膜层.     

Study on the anodic film formation process of AZ91D magnesium alloy

The formation of anodic film of AZ91D magnesium alloy has been investigated by means of electrochemical impedance spectroscopy (EIS), cyclic voltammetry, anodic polarization curve, current-time transients and SEM technique. The results show that, under our experimental conditions, the formation of AZ91D anodic film follows the mechanism of 3D nucleation with diffusion controlled growth. With the increase of applied anodizing potential, the nucleation type of anodic film changes from progressive to instantaneous. The results also show that the initially formed anodized film is threadlike and porous, and high potential is essential for the formation of good anodic film with excellent properties.     

The anodic behaviour of zinc in KOH solution. V: Galvanostatic polarization with an interruption

Galvanostatic polarization experiments, in which the current flow is interrupted and re-established, show that the process of passivation is controlled by the transport of mass in the solution phase.Part IV: M. J. Brook and N. A. Hampson,Electrochim Acta 15 (1970) 1749.