电沉积参数对钛沉积层耐蚀性的影响

为了确定NaCl-KCl-NaF-TiO_2熔盐体系中直流电沉积参数对碳钢表面钛沉积层耐蚀性的影响,分别选取不同的沉积时间和沉积电流进行电沉积钛实验。将沉积后的试样进行交流阻抗测试。通过分析交流阻抗的等效电路可知:在沉积时间1.0h、沉积电流1.5A的条件下获得的钛沉积层的耐蚀性最好。能谱分析表明:钛沉积层的耐蚀性与其表面钛的质量分数有关。     

铁氧化菌对20钢在模拟油田采出液中电偶腐蚀的影响

采用丝束电极测试、耦合电流测试、电化学阻抗谱测试等电化学方法，结合表面形貌分析技术，研究了模拟油田采出液中铁氧化菌(IOB)对CaCO₃+SiO₂沉积层覆盖金属与裸金属之间电偶腐蚀行为的影响。结果表明，IOB增强了沉积层覆盖金属与裸金属之间的电偶效应。在丝束电极测试中，浸泡前6 d内IOB体系的峰值电流密度小于无菌体系，但随着浸泡时间的延长出现反转。电化学阻抗谱测试表明沉积层覆盖金属作为阳极，其表面保护层较为疏松，而裸金属作为阴极，其表面保护层较为致密。IOB促进了沉积层覆盖金属的局部腐蚀，抑制了裸金属的局部腐蚀。     

表面粗糙度对氧化锆固体电解质电性能的影响

介绍了交流阻抗谱技术对不同表面粗糙度的氧化锆固体电解质的电性能的研究,利用3YSZ粉体,分别制备出三种表面粗糙度的样品:抛光机粗抛15min,磨床磨削,1mol/L的硫酸腐蚀表面3.5h。然后涂覆上铂电极,分别测试出其交流阻抗谱图,然后利用电化学阻抗拟合软件Z-VIEW对交流阻抗谱图进行拟合,探讨了粗糙度对其阻抗的影响。实验表明,表面经过粗抛的样品的体阻抗最小。     

Co-Ni-Cu合金镀层的电沉积机制及性能研究

使用循环伏安曲线和交流阻抗谱,研究了柠檬酸体系中Co-Ni-Cu合金镀层的电沉积机制。同时,研究了电流密度对Co-Ni-Cu合金镀层的表面形貌、成分、结合力、耐磨性及表面粗糙度的影响。结果表明:在不同电位下金属离子以不同的状态发生还原,并且钴镍还原反应首先生成吸附性产物M(OH)_(ads),然后在电极表面进一步还原为原子态。当电流密度为3.47 A/dm~2时,Co-Ni-Cu合金镀层形成均匀、细小的晶粒,表面粗糙度最小,结合力与耐磨性最好。     

氨基磺酸体系Co-Ni合金电化学共沉积行为及动力学机理

通过稳态阴极极化和电化学交流阻抗(EIS)等方法,研究了在不同钴镍金属离子比例的氨基磺酸电解液中,Co-Ni合金的电化学共沉积行为。结果表明在氨基磺酸体系中,导致Co-Ni合金异常共沉积行为的原因和在硫酸盐,或氯化物体系中的不同。不是由于Co^2 抑制了Ni的沉积,而是由于NH2SO3^-作为双齿配体形成的异核络合物在电极表面吸附,阻滞了镍离子的还原过程。并且以晶体场理论为基础解释了Co^2 和NH2SO3^-形成的高自旋络合物,比Ni^2 所形成的络合物具有较高的晶体场稳定化能(CFSE),容易分解。因此吸附在电极表面的氨基磺酸根离子对Co2^2 沉积的阻滞作用小于对Ni2^ 的。这样就导致了在氨基磺酸电解液体系中Co^2 的优先沉积。阳极线性扫描曲线表明．钴镍合金中镍含量越高,沉积层在热力学上越稳定,耐蚀性也越好。同时通过EIS的测试,利用等效电路的分析方法和交流阻抗谱解析理论,提出了氨基磺酸电解液中Co-Ni合金共沉积的动力学机理,较好地解释了实验结果。     

柠檬酸钠体系中Ni・Fe合金的电沉积行为

采用循环伏安曲线、电化学阻抗谱、计时电流曲线等方法对柠檬酸钠体系中Ni-Fe合金的电沉积行为进行了研究。结果表明:柠檬酸钠体系中Ni-Fe合金电沉积是一个受扩散控制的不可逆过程。随着电位的增大,电沉积依次经历了电化学活化阶段、电结晶成核阶段、动力学-扩散混合控制阶段和扩散控制阶段。阴极附近未被及时消耗的FeOH+会覆盖在电极表面,阻碍金属离子扩散到电极表面放电,使电化学阻抗谱低频端存在阻挡层扩散阻抗特征。随着电位的增大,Ni-Fe合金的成核速率逐渐加快。Ni-Fe合金的成核机制在低电位下表现为连续成核,在高电位下表现为瞬时成核。     

锡阴电极的制备及析氢性能的研究

为了提高锡电结晶过电位,改善锡镀层表面形貌和制备较好的镀锡电极,通过电镀技术在室温条件下制备了不同电镀液条件下的锡镀层,运用线性伏安法、交流阻抗法和电势阶跃法等电化学方法和SEM技术研究了酸性镀锡体系中明胶对锡沉积的影响。阴极极化曲线和交流阻抗曲线表明,明胶能增大锡沉积反应的电荷传递内阻,提高锡电沉积过电位,延缓锡电沉积反应。电势阶跃表明,锡的电结晶过程遵循扩散控制瞬时成核和三维生长方式的结晶机理。SEM分析结果表明,添加明胶能使锡镀层光滑致密、晶粒细小。电极的极化曲线表明,镀锡电极能提高析氢电位,其中添加明胶所得的锡电极的析氢效果最好。     

亚硒酸在氰化物镀银中的催化作用

本文采用旋转圆盘电极技术与交流阻抗技术对亚硒酸在氰化物镀液中银电沉积过程时的行为进行了研究。结果表明不发生亚硒酸中的硒与银的共同电沉积,但能增大交换电流密度,减小电化学极化电阻,并使交流阻抗谱出现吸附环。据此提出了亚硒酸根离子的吸附催化作用,能形成较易在阴极还原的活性中间物Ag_2SeO_3。     

固定化活性氧化镧除磷的实验研究

采用电沉积法实现镧的固定,利用固定后的氧化镧去除污水中低浓度的磷酸盐,研究了不同电流、电沉积时间、温度、pH和电解液浓度条件下的除磷效果。通过显微镜观察除磷后的电极表面,以分光光度法测量除磷率,最佳除磷效果为97.2%。     

电沉积Ni-P-ZrO2复合电极析氢电催化性能的研究

用电沉积方法制备了镍－磷－二氧化锆复合电极。通过阴极极化曲线,交流阻抗等电化学技术研究其析氢催化性能,并用扫描电镜观察电极的表面形貌。实验结果表明,在80℃,25％氢氧化钠碱性溶液中镍－磷－二氧化锆的表观交换电流密度及表面粗糙度皆大于镍,镍－磷电极,而反应电阻较小。说明镍－磷中引入二氧化锆所形成的复合镀层具有较高的析氢催化活性和良好的电化学稳定性。     

The effects to the structure and electrochemical behavior of zinc phosphate conversion coatings with ethanolamine on magnesium alloy AZ91D

This paper discussed a zinc phosphate conversion coating formed on magnesium alloy AZ91D from the phosphating bath with varying amounts of ethanolamine (MEA). The effects of MEA on the form, structure, phase composition and electrochemical behavior of the phosphate coatings were examined using an scanning electron microscopy (SEM), X-ray diffraction (XRD) potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements. Interpretations of the electrical elements of the equivalent circuit were obtained from the SEM structure of the coatings, assumed to be formed of two layers: an outer porous crystal layer and an inner flat amorphous layer. The result showed that adding MEA refined the microstructure of the crystal layer and that the phosphate coating, derived at the optimal content of 1.2 g/L, with the most uniform and compact outer crystal layer provided the best corrosion protection.     

Comparison of electrochemical behavior of CrN single-layer coating and Cr/CrN nanolayered coating produced by cathodic arc evaporation physical vapor deposition

The aim of the present work is to study the CrN single-layer coating and the Cr/CrN nanolayered coating by cathodic arc evaporation physical vapor deposition (CAE-PVD) on AISI 304 stainless steel and to assess the electrochemical behavior of the coatings. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) were utilized to study the morphology and microstructure of the coatings. The mechanical behavior of the coatings was studied by the nanoindentation technique. The electrochemical behavior of the formed coatings in 3.5 wt.% NaCl solution was investigated via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests. Based on the microscopic images, it was realized that both CrN and Cr/CrN coatings were formed having a dense structure on the substrate. The results of EIS measurements showed gradual changes in the polarization resistance of the Cr/CrN nanolayered coating during the immersion time. However, significant changes in the polarization resistance of the CrN single-layer coating were seen by increasing immersion time comparing with the Cr/CrN coating. The higher polarization resistance of the Cr/CrN coating can be attributed to the effects of the interface between the layers in comparison to the CrN coating.     

Electrochemical impedance spectroscopic characterization of titanium during alkali treatment and apatite growth in simulated body fluid

Alkali treatment of titanium with subsequent heat treatment has been adapted as an important pre-treatment procedure for hydroxyapatite formation in orthopaedic applications. The electrochemical study during the alkali treatment process has not been explored yet. In the present work, electrochemical impedance spectroscopic (EIS) studies have been employed to analyse the electrochemical behaviour of titanium during the alkali treatment. The open circuit potential and potentiodynamic polarisation measurements were carried out in simulated body fluid (SBF) solution. Scanning electron microscopy and energy dispersive X-ray analysis were used to characterize the surface morphology and to correlate the results obtained from the electrochemical studies. An optimum growth of the passive film was found to occur at the end of 17th hour of treatment by alkali treatment. The alkali treated titanium immersed in SBF solution for various durations exhibited the formation of a duplex layer structure due to an inner barrier layer and an outer gel layer during the initial periods of immersion. However, with increase in immersion time to 10 days, a stable apatite layer was formed over the barrier layer and this was confirmed from the equivalent circuit fitted for the impedance data.     

Determination of the adhesion properties of an alkyd pigmented coating by electrochemical impedance spectroscopy

One of the most modern methods of characterizing the electrical properties of coatings is by electrochemical impedance spectroscopy (EIS). EIS can provide useful information about the transport of water and corrosive species through a coating. In this study, impedance measurements were performed in different frequency ranges at open circuit potential for an alkyd coating with TiO₂ as a mineral pigment in 3% NaCl. The most probable impedance equivalent circuit method (MPI) was considered for data analysis. The interpretation of the impedance spectra permitted the determination of water permeation, the formation of blisters, swelling of the coating, and the loss of adhesion.     

Corrosion‐protection aspects of electrochemically synthesized poly(o‐anisidine) coatings on mild steel: An electrochemical impedance spectroscopy study

The corrosion‐protection aspects of poly(o‐anisidine) (POA) coatings on mild steel in aqueous 3% NaCl solutions were investigated with electrochemical impedance spectroscopy, a potentiodynamic polarization technique, and open circuit potential measurements. The POA coatings were electrochemically synthesized on mild steel with cyclic voltammetry from an aqueous salicylate medium. The corrosion behavior of the POA coatings was investigated through immersion tests performed in aqueous 3% NaCl solutions, and the recorded electrochemical impedance spectra were fitted with an equivalent circuit to obtain the characteristic impedance parameters. The use of a single equivalent circuit was inadequate to explain the various physical and electrochemical processes occurring at different exposure times. It was suggested that some characteristic element(s) should be incorporated into the equivalent circuit at different stages of the immersion to elucidate the various processes occurring at different exposure times. The evolution of the impedance parameters with the immersion time was studied, and the results showed that POA acted as a protective coating on the mild steel against corrosion in a 3% NaCl solution. From these data, the water uptake and delamination area were determined to further support the corrosion‐protection performance of the POA coating. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Study on corrosion resistance and roughness of micro-plasma oxidation ceramic coatings on Ti alloy by EIS technique

Micro-plasma oxidation (MPO) technique has been developed quickly in recent years. The produced ceramic coatings are reported to possess fine properties and promising application prospects in many fields. The aim of this work is to study the corrosion resistance and the roughness of the micro-plasma oxidation ceramic coatings on Ti alloy by electrochemical impedance spectroscopy (EIS) technique. Compound ceramic coatings were prepared on Ti-6Al-4V alloy by pulsed bi-polar micro-plasma oxidation in NaAlO₂ solution. The phase composition and element distribution in the coating were investigated by X-ray diffractometry and electron probe micro-analyzer. EIS of the coatings was measured through CHI604 electrochemical analyzer in 3.5% NaCl solution. The ceramic coating is composed of a large amount of Al₂TiO₅ and a little α-Al₂O₃ and rutile TiO₂. The coating is of double-layer structure with the loose outer layer and the dense inner layer. The thickness of the coatings is reduced when the working frequency or the cathode pulse current density is increased, while the thickness is increased when the frequency or the anode current density is increased. The established “equivalent circuit” of the coatings is consistent with the double-layer structure. The electric charge transfer resistance (R_t) in the equivalent circuit can be used to assess the corrosion resistance of the coatings, which is consistent with the result of the polarizing curves test. And the empirical exponent (n₁) of the constant phase element (Q₁) in the equivalent circuit can be used to assess the surface roughness of the coatings, which is consistent with the surface SEM analysis of the coatings.     

Corrosion tests of nickel coatings prepared from a Watts-type bath

This paper deals with the preparation and characterization of thin Ni layers. The electrodeposition was carried out galvanostatically from a Watts bath at different current densities in the range from 1 to 10 A dm⁻² and for deposition times between 900 and 7200 s. The structure and the morphology of the nickel coatings were investigated by SEM and XRD techniques. The microhardness of deposited layers, the electrochemical behavior and the corrosion properties of the deposits were investigated by means of Vickers microhardness, polarization measurements, and electrochemical impedance spectroscopy (EIS). The uniform deposits showed fine grains and good protection against corrosion.     

用电化学阻抗谱技术研究储油罐涂层的安全防护寿命

采用电化学阻抗谱(EIS)研究了不同孔径环氧导静电涂层的电化学特性,获得了储油罐内防护涂层逐渐遭受破坏的电化学阻抗变化规律.结果表明,EIS谱图中10mHz频率处103～104 Ω的总阻抗值是判定环氧导静电涂层防护性能失效的依据.     

Electrochemical behavior of cobalt oxide coatings on cold-rolled steel in alkaline sodium sulfate

The electrochemical behavior of a coating of cobalt oxide on cold-rolled steel in alkaline sodium sulfate was studied using the electrochemical techniques of open-circuit potential measurements and electrochemical impedance spectroscopy. The coating was prepared at different annealing temperatures ranging from 350 to 750 °C and characterized by SEM, EDX and XRD. Below 550 °C the composition of the coating was basically of Co₃O₄. At 750 °C CoO was formed and big cracks appeared on the film exposing an inner layer of iron oxides. Analysis of the EIS data is very difficult because of the complexity of the interface structure. It can be inferred that the charge transfer resistance of the coatings prepared at 350 and 450 °C were higher than those for the coatings prepared at temperatures above 550 °C.     

类金刚石薄膜在模拟体液中的电化学阻抗

利用双放电腔微波等离子体源全方位离子注入设备,分别采用等离子体增强化学气相沉积技术、等离子体源离子注入和等离子体增强化学气相沉积复合技术两种工艺对医用3161,不锈钢进行类会刚石薄膜表面改性。利用电化学阻抗谱法考察了两种工艺制备的类金刚石薄膜在模拟体液中的抗腐蚀性能。结果表明：与采用等离子体增强化学气相沉积技术制备的类金刚石薄膜相比,在72h的浸泡时间内,采用等离子体源离子注入和等离子体增强化学气相沉积复合技术制备的类金刚石薄膜防腐蚀性能明显增高,腐蚀阻抗较高,碳注入层可有效抑制溶液渗入薄膜和基体之间的界面,起到了腐蚀防护层的作用。动电位极化测试表明：采用复合技术制备的类金刚石薄膜在模拟体液中的腐蚀倾向性更低,钝态稳定性更好。