共查询到20条相似文献,搜索用时 15 毫秒
1.
Khaled M. Ismail Ahlam M. Fathi Waheed A. Badawy 《Journal of Applied Electrochemistry》2004,34(8):823-831
The electrochemical behaviour of copper–nickel alloys with different Ni content (5–65%) in sulphate solutions of pH 12 was investigated. The effects of temperature, immersion time, and concentration of sulphate ions were also studied. Different electrochemical methods such as open-circuit potential measurements, polarization techniques and electrochemical impedance spectroscopy (EIS) were used. Potentiodynamic measurements reveal that the increase in nickel content increases the corrosion rate of the alloy in sulphate solution linearly. Nevertheless, an increase in the nickel content along with increase in immersion time improves the stability of the Cu–Ni alloys due to the formation of a stable passive film. An equivalent circuit model for the electrode/electrolyte interface under different conditions was proposed. The experimental impedance data were fitted to theoretical data according to the proposed model. The relevance of the model to the corrosion/passivation phenomena occurring at the electrode/solution interface was discussed. 相似文献
2.
Effect of alternating voltage passivation on the corrosion resistance of duplex stainless steel 总被引:2,自引:0,他引:2
Huan He Tao Zhang Chengzhi Zhao Kai Hou Guozhe Meng Yawei Shao Fuhui Wang 《Journal of Applied Electrochemistry》2009,39(5):737-745
Potentiodynamic polarization and E
corr versus t curves were obtained, together with electrochemical impedance spectroscopy (EIS) measurements, in order to understand the
effects of alternating voltage (AV) passivation on the corrosion resistance of duplex stainless steel (DSS). SEM, EDS and
XPS were employed to further investigate the influence of AV passivation on the properties of the passive film. The results
of the electrochemical measurements showed that AV passivation significantly improved the corrosion resistance of DSS. SEM
images indicated that the surface exhibited a unique morphology after AV passivation treatment, and XPS results suggested
that AV passivation greatly increased the thickness of the passive film. Furthermore, significant chromium enrichment and
a higher ratio of Fe3+/Fe2+ were observed in the passive film after AV passivation. Mott–Schottky results confirmed that AV passivation had a strong
influence on the semiconducting properties of the passive film. 相似文献
3.
Titanium (Ti) exhibits excellent corrosion resistance in most aqueous media due to the formation of a stable oxide film and
is chosen for surgical and odontological implants for this resistance and its biocompatibility. Treatment with fluorides (F)
is the main method to prevent plaque formation and dental caries. Toothpastes, mouthwashes and prophylactic gels can contain
from 200 to 20,000 ppm F and have neutral to acidic character, which can affect the corrosion behavior of titanium devices
present in the oral cavity. In this work the behavior of Ti has been evaluated in artificial saliva of pH 2, 5 and 7 and different
fluoride concentrations (0, 1,000, 5,000 and 10,000 ppm F), through open-circuit potential measurements, potentiodynamic polarization
and electrochemical impedance spectroscopy. Limits of pH value and fluoride concentration at which Ti corrosion behavior changed
could be established. Active behavior was observed for pH 2 and 1,000–10,000 ppm F, and for pH 5 and 5,000 and 10,000 ppm
F. The other conditions led to passive behavior. Decrease in corrosion resistance and less tendency for passivation were observed
as fluoride concentration increased and pH decreased. 相似文献
4.
Valéria A. Alves Luís A. da Silva Luís F. de F. Santos Dane T. Cestarolli Alexandre Rossi Leonardo M. da Silva 《Journal of Applied Electrochemistry》2007,37(8):961-969
The electrochemical behaviour of biomaterials based on Cu–Zn–Al (cubic Cu3Zn phase) and Ag–Sn (orthorhombic Ag3Sn and hexagonal Ag4Sn phases) alloys was investigated in carbonate buffer solutions (pH 9.66) in the absence and presence of chloride, using
different electrochemical techniques. Analyses of the open circuit potential and the potentiodynamic polarisation curves showed
that the passivation domain and the corrosion parameters depend on alloy composition and chloride concentration. Chronoamperometric
studies showed that passivation kinetics and corrosion of the passive film are both well described by a linear ln(i) versus ln(t) relation. The passive film formed on the Ag–Sn alloy is less susceptible to corrosion when compared to the Cu–Zn–Al system.
The impedance data obtained in the passive region for the Cu–Zn–Al alloy showed that the passive layer is compact. In contrast,
the impedance data obtained for the Ag–Sn alloy showed that the passive layer is formed by a compact oxide layer covered by
a porous oxide gel layer. Mott–Schottky analysis showed that the passive film formed on the Cu–Zn–Al alloy behaves as a p-type
semiconductor. 相似文献
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为了解铝在锂盐溶液中的钝化行为,通过失重法研究了溶液pH值、温度、浸泡时间及氯离子浓度等因素对钝化膜形成及稳定性的影响。结果表明,溶液pH值和温度对钝化膜的和稳定性影响最大。为获得稳定的钝化膜,锂离子的浓度应随pH值的增大而增大,含锂钝化膜对氯离子的局部腐蚀有较强的抑制作用。 相似文献
7.
The passivation and pitting corrosion of tin-nickel alloy (34% Ni-66% Sn) in NaCl solution was studied using potentiodynamic, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques complemented by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of concentration of the chloride ion, the switching potential, scans rate and pH on the electrochemical behavior of Sn-Ni alloy is discussed. The data indicate that the corrosion rate and the pitting corrosion of Sn-Ni alloy increases by the increasing of chloride ion concentration. The observed corrosion resistance of electrodeposited Sn-Ni alloy is due to the formation of a thin passive film from tin and nickel oxides. 相似文献
8.
Mechanical and electrochemical behavior of nanocrystalline surface of 304 stainless steel 总被引:1,自引:0,他引:1
This paper reports our recent studies on nanocrystalline surface layer of 304 stainless steel (304SS) produced using a sandblasting and annealing process. The grain size of the sandblasted surface layer was less than 20 nm. Mechanical and electrochemical properties of the nanocrystalline surface and its passive film were investigated using nano/micro/-indentation, micro-scratch, scanning Kelvin probe (SKP), potentiodynamic scanning and electrochemical scratch techniques. It was demonstrated that the nanocrystalline surface was markedly superior to that of original 304SS with enhanced passive film. The polarization, electrochemical scratch and SKP measurements indicated that the nanocrystalline surface had higher resistance to corrosion, greater capability of repassivation and higher chemistry stability. All results demonstrated that the nanocrystallization surface did not only enhance the mechanical properties of the surface layer and its passive film, but also benefited the passivation capability of the steel with improved corrosion resistance. 相似文献
9.
Waheed A. Badawy Rabab M. El-Sherif Hassan Shehata 《Journal of Applied Electrochemistry》2007,37(10):1099-1106
The electrochemical behavior, especially the corrosion and passivation, of a Cu–Al bronze was investigated. Conventional electrochemical
techniques including open-circuit potential, anodic polarization, cyclic voltammetry and electrochemical impedance spectroscopy
were used. It was found that the addition of chloride ion up to 0.15 M in 0.5 M Na2SO4 solution decreases the corrosion rate due to the formation of CuCl, whereas at higher concentration of the chloride ion,
the corrosion rate increases due to the formation of the soluble CuCl2−. The activation energy was found to be 10 kJ mol−1. This value indicates that the corrosion process is under diffusion control. The impedance measurements showed that the passive
film can be represented by a duplex layer, a relatively thick porous outer film on top of a thin compact layer. An equivalent
circuit was used to explain and analyze the impedance data. The model includes another R-C combination and Warburg impedance
in addition to the simple Randles cell to account for the spontaneously formed passive film and the diffusion phenomena. 相似文献
10.
The electrochemical behavior of the Cu-10Al-5Ni alloy in simulated electrolytes like those used in the industrial processes under normal working conditions was investigated. Conventional electrochemical techniques including open circuit potential measurements, polarization techniques, and electrochemical impedance spectroscopy were used. The alloy was found to be more stable against corrosion when the chloride-sulfate solution had a pH of 7-9. A sulfate concentration of ≅0.1 M in the chloride-sulfate electrolyte leads to the passivation of the alloy surface. The activation energy of the corrosion process was found to be 8 kJ mol−1 assigning a diffusion controlled reaction. The impedance measurements and impedance data fitting to equivalent circuit models have shown that the passive film posses a duplex nature. 相似文献
11.
研究了三价铬钝化液的pH值对锌-镍合金钝化膜的形成机理、耐蚀性、表面形貌的影响。在三价铬钝化过程中,pH值是一个重要的工艺参数,它决定了钝化膜的生成和溶解。当钝化液的pH值过低时,钝化膜的溶解速率过快,使得钝化膜的微裂纹结构不太明显,不利于提高钝化膜的耐蚀性。当钝化液的pH值过高时,钝化液的活性下降,锌的溶解速率降低,影响钝化膜的生长,同样不利于提高钝化膜的耐蚀性。在pH值为2.0的条件下制得的钝化膜具有均匀、致密的微裂纹结构,耐蚀性良好。 相似文献
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Poly(N‐methylpyrrole) coatings were formed on low carbon steel by an electrochemical method from aqueous oxalate solutions. The electrochemical reactions were performed in a wide range of pH of the reaction medium and applied current density. The formation of poly(N‐methylpyrrole) on steel occurred in three stages: (i) dissolution of the steel, followed by (ii) passivation of the steel, and, finally, (iii) electropolymerization of N‐methylpyrrole on the passivated steel. The time taken to form the passive interphase (induction time) is decreased by an increased applied current. Passivation occurred instantaneously at pH 8.4. Below pH 7, the shortest passivation time occurred at pH 2.6. The quantity of the charge consumed during passivation (passivation charge) remained independent of the applied current at pH ≈ 2.6 and decreased with the applied current at pH 4.1 and 5.7. The polymerization potential increased with the pH and the applied current. Polymerization potentials greater than 2.0 V resulted in film degradation. By controlling the electrochemical process parameters, good quality poly(N‐methylpyrrole) was formed at a controlled induction time. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1293–1302, 1999 相似文献
14.
Passive film growth, electrodissolution and pitting corrosion of indium electrodes in NaCl solutions in the pH range 2–12.6 were studied using potentiostatic and potentiodynamic techniques complemented with SEM. In the pH range between 10.5 and 12.6 the oxide formation should involve a mixed control, a surface reaction plus a diffusion process. On decreasing pH the process becomes more complex due to the formation of In(I). The effect of chloride ions upon the active and passive behaviour of indium has been determined. Chloride ions in neutral and alkaline solutions produce pitting at potential values more positive than those of the active—passive transition. Localized corrosion appears to be under a competitive surface mechanism involving the formation of the passive film and the nucleation and growth of an indium chloride salt layer. 相似文献
15.
Utilizing electrochemical impedance spectroscopy (EIS), we characterize the passive film properties of alloy 22 during immersion in low pH nitrate and chloride solutions. In pure HCl, the passive film grows thinner with increasing acid concentration. In contrast, in HNO3, the passive film corrosion protection properties are enhanced, which leads to low corrosion rates, even at pH < −0.5. The combined influence of both HCl and HNO3 in contact simultaneously with the alloy 22 surface shows multiple phases in the passive film properties depending on the pH. EIS results show that the passive film changes either thickness and/or composition as the system is driven chemically through different corrosion states, including: active, passive, active/passive and transpassive. 相似文献
16.
Electrochemical behavior of mild steel in concrete: Influence of pH and carbonate content of concrete pore solution 总被引:1,自引:0,他引:1
The increase of the rebars corrosion rate due to the concrete carbonation is the major cause of reinforced concrete degradation. The aim of this study was to investigate the transition from passive to active corrosion of mild steel rebars in carbonated concrete. For this purpose, electrochemical techniques (polarization curves, free corrosion potential measurements) and surface analyses (EDS, XRD, XPS) were used. Five different electrolytes, with pH ranging from 13 to 8.3, were chosen to simulate the interstitial concrete pore water at various degrees of carbonation. The results indicate that the transition pH is between 10 and 9.4. XPS results indicate a passivation of mild steel for pH values ranging from 13 to 10 due to the formation of a thin iron III oxide layer. Immersion tests highlight the importance of the buffering effect of the carbonate content. At the free corrosion potential in an aerated solution, a decrease of the carbonate content increases the corrosion rate. On the opposite, at low electrode potential, the kinetics of oxidation increases with the carbonate content. 相似文献
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19.
J. A. Caldern O. R. Mattos O. E. Barcia S. I. Crdoba de Torresi J. E. Pereira da Silva 《Electrochimica acta》2002,47(28):4531-4541
The electrodissolution of cobalt in carbonate/bicarbonate solutions was studied at room temperature by steady state polarisation, interfacial pH measurements and Raman spectroscopy. The active dissolution of cobalt leads to an initial CoO film formation. The metal passivation occurs by a slow transformation of the CoO into a Co3O4 oxide. The influence of HCO3− and CO32− anions was investigated. Two different parallel electrochemical processes were proposed to account for the anion role on the electrochemical steady state behaviour of cobalt in the studied solutions. 相似文献
20.
The effect of the passivation potential on the properties of the barrier films formed on high purity aluminium has been examined. The current-time responses were recorded, the charge used during formation of the barrier film was determined, and the steady-state currents were discussed. Impedance measurements provided an insight into the characteristic sizes of barrier films. Equivalent circuits which illustrate the examined aluminium/oxide film/electrolyte systems were proposed and individual circuit elements were defined. The resistance and thickness of the barrier film were shown to increase linearly with increase in the passivation potential, while increase in solution pH caused a marked decrease in the total system impedance. The paper also defines current efficiency in the formation of the barrier film. The value of 20% indicates that the formation of barrier films on aluminium is a process that takes place with considerable current losses. The mechanism of barrier film growth has been examined within the framework of two models suggested by different authors. Both agreements with and differences from the theories proposed have been indicated. 相似文献