Impedance studies of the passive film on aluminium

Impedance spectroscopy has been used to study the characteristics of aluminium in 0.10 M NaCl solution at potentials below the pitting potential (−1.50V_SCE to −0.70V_SCE). Multiple capacitive (or pseudocapacitive) impedance features have been identified and analyzed over this range of potentials. Higher frequency resistances have been compared with surface analytical data, establishing a correlation between higher frequency impedances and the concentration of chloride in the passive film. The relationship shows that both charging resistance and chloride concentration reach a maximum immediately prior to passive film breakdown. At the onset of metastable pitting, both the impedance and chloride concentration decrease from the measured maxima. In contrast to X-ray photoelectron spectroscopy studies, the impedance results do not reveal oxide thinning prior to the onset of metastable pitting. Modelling from impedance data indicates that the thickness of the oxide layer sampled by impedance is much thinner than the oxide measured with surface analytical techniques, suggesting that the impedance method senses only the space charge layer in the oxide and not the total film thickness.     

Impedance of NiSi electrode in sulfuric-acid solution in the region of passive and transpassive states

The behavior of an NiSi electrode in 0.5 M H₂SO₄ in the region of passive and transpassive state (from 0.50 to 2.1 V (versus SHE)) is studied. The conclusion is made about formation of oxide film close to SiO₂ by composition on the electrode surface in the passivation process. Equivalent electric circuit modeling passive and transpassive state of nickel silicide is proposed. Thickness of oxide film and its specific resistance depending on electrode potential are calculated basing on the impedance data.     

Impedance measurements on oxide films on aluminium obtained by pulsed tensions

We have performed this study on oxide films sealed or not in boiling water. The films are first obtained on type 1050 A aluminium substrat by pulsed tensions anodizing technique, in a sulfuric acid solution. Afterwards the, Electrochemical Impedance Spectroscopy (EIS) is employed to appreciate the films behaviour in a neutral solution of 3.5% K₂SO₄, in which the interface processes interest only the ageing phenomenon of the oxide films and not their corrosion. We have also attempted a correlation between pulse parameters of anodization and the electrical parameters characterizing these films. The sealing influence on ageing has been studied as well. For all films, ageing is appreciated using impedance diagrams evolution versus time. The results show: – the existence of two capacitive loops confirming the presence of two oxide layers characteristic of oxide films obtained in a sulfuric acid medium. The first loop, at high frequencies, is related to the external porous layer and the second one, at lower freqencies, is related to the internal barrier layer. – the thickness of the barrier layer varies between 25 and 40 nm in relation with the electrical pulse parameters. – the sealing acts favorably against anodic oxide films ageing.     

New data on the kinetics of passive nickel from very low frequency impedance measurements

An investigation of passive nickel in IM H₂SO₄ and IM H₃PO₄ has been performed. Impedance measurements extended to very low frequencies (10⁻⁴Hz) revealed a substantial control of the passive dissolution of Ni by diffusion and allowed to describe its potential dependence.     

Effect of temperature on the inhibition of the acid corrosion of steel by benzaldehyde thiosemicarbazone: Impedance measurements

An impedance study has been carried out of the corrosion of steel in sulphuric acid containing benzaldehyde thiosemicarbazone as an inhibitor, over the temperature range 25 – 60 °C. The impedance data indicate that the corrosion of steel is controlled by a charge transfer process at all the temperatures examined and in solutions containing various concentrations of the inhibitor. At a critical concentration of the inhibitor (5 × 10^-4 M) a high protection efficiency is maintained over the temperature range examined. This is thought to relate to a high surface coverage of a relatively compact adsorbed film, which resists desorption at elevated temperatures, unlike the behaviour evident at lower inhibitor concentrations.     

AC5型交流阻抗测试系统的建立

本文介绍了作者研制的AC5型电化学交流阻抗测试系统，它的硬件和软件是针对电化学体系而设计的，因而比一般通用型测试系统操作使用方便。AC5型电化学交流阻抗测试系统可用于金属耐蚀性能、缓蚀剂性能和电池等的研究。     

Galvanostatic and potentiostatic measurements on iron dissolution in the range between active and passive state

The kinetics of anodic iron dissolution in sulphate ions containing solutions, which are free of oxygen, were investigated in the range between active and passive states of the metal at pH 5. The measurements were carried out at fixed electrodes under mechanical stirring of the electrolyte at T = 298K using galvanostatic as well as potentiostatic pulse technique. In the prepassive range the obtained transients indicate transition states, which can be attributed to parallel reactions to the active metal dissolution. The mechanism of the metal dissolution in the prepassive range is discussed.     

超声磨削系统等效阻抗模型及负载特性研究

利用力电等效理论建立了磨削用超声换能系统的等效阻抗模型,包括各组成部分的材料特性、尺寸及物理参数。推导了系统谐振频率方程,理论计算和实验研究分析了系统谐振频率受负载的影响特性,结果表明谐振频率随负载增大呈下降趋势变化。研究结果为超声磨削负载控制提供了理论基础。     

挖掘机电液系统的滑模阻抗控制

为了实现挖掘机操作臂的轨迹控制,需要对各关节油缸位置进行控制。建立了挖掘机电液系统的非线性数学模型。由于挖掘机会在自由空间和约束空间运动,因此采用了阻抗控制。又考虑到挖掘机电液系统的非线性和不确定性,因此将变切换函数的滑模控制用于阻抗控制中,使得系统存在不确定性时,控制器仍然能保持较高的控制精度。滑模控制渐进驱动系统状态以执行目标阻抗,在对操作臂进行位置控制的同时进行力控制。针对所设计的控制器进行了仿真,给出了位置跟踪和力跟踪的效果。     

舵机动刚度试验台蓄能器的计算与分析

在舵机动刚度试验中,需要使用力伺服系统模拟外部大气干扰来测试舵机在高频负载力作用下的动刚度性能.而试验台泵站提供的瞬时流量无法达到高频大负载的油量要求,因此必须配置相应的蓄能器以补充瞬间供油量的不足.通过对蓄能器的容量计算,确定了满足试验要求的蓄能器型号及数量.     

舵机动刚度试验台的建模与仿真

对舵机动刚度试验台进行了仿真分析.对舵机动刚度试验台进行建模仿真,通过加载部分给舵机系统部分施加不同频率的干扰力,观察并记录在不同频率下的舵机位置系统的输出,进而得出系统的动刚度特性.通过分析舵机位置系统的动刚度特性验证了该试验台的可行性与合理性,改变舵机系统的参数并观察参数对动刚度特性的影响,得到了很好的指导结果,同时也为舵机动刚度试验台的研制提供了依据.     

100t高阻抗电弧炉的自动化控制系统

介绍了采用西门子公司PCS7系统为核心的高阻抗电弧炉自动化控制系统,主要包括有高阻抗电弧炉的主要设计技术参数,控制系统的硬件设计方案及组成,自动化系统的软件设计功能和主要控制对象,按照铸造生产对控制系统的要求,将整个系统划分为若干个控制子单元分别进行功能描述,详细说明了各部分的控制范围及目的,使得该套高阻抗电弧炉的控制系统能够在铸造生产的过程中全面实现工业现代化的操作、监控、信息处理和检修维护,保障了铸造生产设备的安全运行。     

60t高阻抗电弧炉供电制度优化

根据高阻抗电弧炉电气设计原理及60 t电弧炉基础设计数据,对其供电模式进行重新计算与优化,使热效率提高,平均吨钢电耗降低约44 k Wh,经济效益显著。     

Impedance measurements of corroding mild steel in an automotive fuel ethanol with and without inhibitor in a two and three electrode cell

The impedance measurements in a highly resistive electrolyte medium are difficult. The use of two identical electrode cells having a large surface area may overcome this difficulty, but measurements have to be restricted to the corrosion potential. The advantages of each type of cell are discussed. The electrochemical system tested in this work was the corrosion of mild steel in an automotive fuel ethanol with or without ethanolamines as corrosion inhibitors. It was found that in a three electrode cell, the use of a special electronic circuit increasing the input impedance of reference electrode was necessary to perform correct measurements. No particular care was needed in the impedance measurements in a two electrode cell. If the two electrode plates were set too close, the measured impedance was significantly great, thus leading to an erroneous prediction of the corrosion behaviour. A tentative explanation to this phenomenon is given.     

Electrochemical Impedance Spectroscopy of protective coatings

Electrochemical impedance spectroscopy (EIS) carried out over a wide frequency range (10⁵ to 10^?2 Hz) allows us to obtain mechanistic information concerning corrosion protection by coatings. Examples are given for polymer coatings on an Al alloy as a function of surface petreatment and for anodized Al alloys. For polymer coatings on metals, information concerning the coating's properties and its changes with exposure time can be obtained from the high and medium frequency regions of the impedance spectrum, while the corrosion reaction at the metal/coating interface can be evaluated from the low frequency part. The pore resistance of the coating and its changes with exposure time have been used to rank different pretreatment procedures for a given metal/coating combination. For Al alloys, pronounced differences in corrosion resistance between a conversion coating and an anodized layer under a polyurethane coating have been observed. The use of a segmented electrode allows measurements of the impedance across as well as under a coating. From these data, information concerning delamination can be obtained. An example is given for an epoxy coating on steel. The use of EIS as a quality control and corrosion test for anodized Al alloys is discussed. The effects of the anodization procedure (sulfuric acid and chromic acid), sealing procedure (hot water and dichromate) and alloy chemistry (Al 2024, 6061 and 7075) have been studied during exposure to aerated 0.5 N NaCl. All these parameters play an important role in the corrosion resistance of the alloys. The sealing process can be evaluated from the high frequency part of the spectrum. Pronounced differences in the spectra for the two sealing procedures are observed. The corrosion behavior is reflected in the low frequency part, which is essentially dominated by barrier layer properties.     

Impedance spectroscopy of the process of hard anodizing of aluminum alloys

This article discusses an in situ method for the diagnostics of the hard anodizing process based on impedance spectroscopy allowing the coating thickness during treatment to be estimated. The experimental results are given for the hard anodizing of aluminum alloys used in the aircraft industry. Parameters of an equivalent circuit of the electrolyzer were specified and the regularities of their evolution were established. A diagnostic model was proposed and its efficiency was demonstrated for an industrial serial production.     

Impedance investigation of the anodic iron dissolution in perchloric acid solution

The anodic iron dissolution in 0.5 mol dm⁻³ perchloric acid (HClO₄) was investigated by the electrochemical impedance spectroscopy, the potentiodynamic sweep and the scanning electron microscopy measurements. The anodic polarization behavior of iron in HClO₄ solution showed that the strong current oscillations occurred in a narrow potential region, particularly the pitting corrosion was observed in the active dissolution region. These characteristics were quite different from those of iron in the sulfuric acid (H₂SO₄). At the potentials 82 and 132 mV more positive than the corrosion potential (−482 mV vs. SCE), the impedance spectra for the iron in HClO₄ displayed two inductive arcs; however, by gradually increasing potential the lower frequency inductive arc disappeared at −300 mV at first, and then the higher frequency inductive arc changed into a capacitive arc at −250 mV. Based on the impedance display of iron at various potentials, a reaction model involving two adsorbed intermediate species was proposed, in terms of which the impedance behavior at different potentials were described. Occurrence of the pitting corrosion in active dissolution region was explained.     

机器人的阻抗控制

阻抗控制在机器人的力的控制中具有重要地位,文章对阻抗控制方法中的参数的意义进行了说明,总结并分析对比了阻抗控制和其它力控方法的特点,对基于动力学模型和基于位置的两种主要的阻抗控制方法进行了分析,列出了阻抗控制参数的选取方法.