The stability of the passive state of iron–chromium alloys in sulphuric acid solution

Bojinov, Martin; Betova, Iva; Fabricius, Gunilla; Laitinen, Tarja; Saario, Timo

doi:10.1016/s0010-938x(99)00003-7

“…With the immersion time of 432 h, the diameter of capacity loop became bigger again, and then the impedance value still remained large, indicating that the Ni-Co-TiO 2 composite coating still provided good protection for the NdFeB magnet after 432 h immersion in neutral 3.5 wt% NaCl solutions. At the initial stage of the immersion test, the increase in impedance value can be ascribed to the formation and growth of the passive film on the metal surface [17,[32][33][34][35], and indicated the thickening and compaction of the passive film. After the immersion for 240 h, the decrease in impedance value may be resulted from the fact that the passive film suffered from the attack of corrosive medium, e.g., chloride ions, resulting in decrease in thickness and increase in defect.…”

Section: Long-term Immersion Testmentioning

confidence: 99%

Electrochemical corrosion behaviors and protective properties of Ni–Co–TiO₂ composite coating prepared on sintered NdFeB magnet

Yang

¹

,

Li

²

,

Zhang

³

et al. 2010

Materials & Corrosion

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In this paper, a protective Ni-Co-TiO 2 composite coating was prepared on the sintered NdFeB magnet by direct current electrodeposition. The surface morphologies, microstructure, and chemical composition of the composite coating were studied using scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS), respectively. The surface morphologies and microstructure analysis showed that the composite coating possessed cauliflower-like grain colonies, and formed face-centered cubic (fcc) solid solution. The electrochemical corrosion behaviors of the composite coating in 0.5 mol/L H 2 SO 4 , 0.6 mol/L NaOH, 0.6 mol/L Na 2 SO 4 , and neutral 3.5 wt% NaCl solutions were evaluated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS), showing good protection for NdFeB magnet. In order to further investigate the protective properties of the composite coating for NdFeB magnet and the practicability of the composite coating, the long-term immersion test was carried out in neutral 3.5 wt% NaCl solutions using EIS. The results of long-term corrosion test showed that the Ni-Co-TiO 2 composite coating could provide long-term protection in neutral 3.5 wt% NaCl solutions for NdFeB magnet.

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“…Em geral, há um consenso (Castle e Clayton, 1977, Ginesan e Smith, 1988, Hakiki et al, 1995, Bojinov et al, 1999, Martini e Muller, 2000, Montemor et al, 2000, Oh et al, 2004 sobre o caráter duplex dos filmes passivos sobre aços inoxidáveis. Estes filmes geralmente apresentam gradientes de composição química e podem ser constituídos de regiões com propriedades semicondutoras diferenciadas (Hakiki et al, 1995, Martini e Muller, 2000, Montemor et al, 2000.…”

Section: Resistência à Corrosão E Camada Passivaunclassified

“…A literatura (Hakiki et al, 1995, Bojinov et al, 1999, Montemor et al, 2000, Abreu et al, 2006, Antunes, 2006 propõe que a camada passiva dos aços inoxidáveis é constituída por uma camada duplex, na qual o óxido mais interno é rico em cromo, e o óxido mais externo é rico em ferro e níquel. Os resultados do presente trabalho estão de acordo com a literatura no que diz respeito à presença de duas constantes de tempo, indicada pelos resultados dos ajustes dos diagramas a um circuito equivalente com duas constantes de tempo (Anexos 1 e 2).…”

Section: Din W Nr 14970unclassified

“…Esta camada é composta de uma camada interna, rica em cromo, e outra externa, rica em ferro e níquel (Hakiki et al, 1995, Bojinov et al, 1999, Montemor et al, 2000, Abreu et al, 2006, Antunes, 2006.…”

Section: Din W Nr 14575unclassified

“…Dentre todos os modelos testados, os quais já foram propostos anteriormente (Azumi et al, 1986, Bundy et al, 1993, Montemor et al, 2000, Liu et al, 2003, Antunes, 2006 (Hakiki et al, 1995, Bojinov et al, 1999, Montemor et al, 2000, é formado por uma camada externa rica em óxido de ferro (Fe 2 O 3 ) e outra interna de óxido de cromo (Cr 2 O 3 ). Trabalhos recentes mostram ainda que a presença de níquel pode inibir os processos de oxidação do ferro e do cromo, diminuindo a espessura da película de óxido formada ao ar.…”

Section: Circuitos Elétricos Equivalentesunclassified

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Corrosão de aços inoxidáveis avançados em meios fisiológicos

Terada¹

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were rich in chromium and iron. The electrochemical behavior of these steels was investigated using electrochemical impedance spectroscopy (EIE), potentiodynamic polarization, scanning vibrating electrode technique (SVET), field emission gun (FEG), scanning electrochemical microscopy (SECM), optical microscopy (OM) and scanning electron microscopy (SEM). The test electrolytes used were Hanks solution, a culture medium known as Minimum Essential Medium (MEM) and a buffered phoshated solution (PBS). The EIE results were interpreted using equivalent electrical circuits that simulated the duplex structure of the oxide layer. All the materials were more resistant to localized corrosion than AISI 316L, with composition similar to ASTM F-138 SS. The results also highlighted the effect of the solution annealing treatment on corrosion resistance of the high nitrogen DIN W. Nr. 1.4460.The DIN W. Nr. 1.4970 steel was cytotoxic. Hence it cannot be used as a biomaterial.The DIN W. Nr. 1.4575 steel and Incoloy MA 956 can only be used for applications of easy removal, such as for odontological prostheses, due to their ferromagnetic properties. The DIN W. Nr. 1.4460 (0.87% nitrogen) steel was the SS with the best properties, among those studied for use as biomaterials.

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Passivity of Metals, Alloys, and Semiconductors

Schultze

¹

,

Hassel

²

2003

Encyclopedia of Electrochemistry

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The sections in this article are Introduction Definition of Passivity Survey of Systems General Principles of Passivity Thermodynamics and Bond Polarity Experimental Techniques for Characterization of Passive Films Thickness and Stoichiometry of Passive Films Chemistry, Crystal Structure and Aging Chemistry and Crystal Structure Aging Potential Distribution at the Interface Electrochemical and Chemical Reactions in Passive Systems Reactions Current Densities i Ionic Properties, Migration and Ion‐Transfer Reactions Electronic Behavior and ETR Band Structure of Oxide Films Electron‐Transfer Reactions ETR at Oxide Films Mixed Ionic/Electronic Conductivity Equivalent Circuit Diagrams Growth of Oxide Films and Ionic Migration Survey on the Growth of Oxide Films Insulating Passive Films on Metals: Growth, and Corrosion of Al as Example Thermodynamic Aspects A Survey on Oxide Formation from CVs The Film Formation Factor k Electrochemical Impedance Spectra EIS and Equivalent Circuit Diagram Kinetics of Film Growth Corrosion and Breakdown Porous Aluminum Oxide Other Types of Passive Aluminum Oxide Films, Anof, Modified Aluminum, Alloys Other Systems Other Metals Forming Insulating Oxide Films Semiconducting and Metallic Oxide Films on Metals Duplex Films Passivation with Participation of the Electrolyte Semiconductors Passivation of Alloys ITR at the Homogeneous Oxide/Electrolyte Interface: Corrosion and Modification Passive Corrosion in the Steady State Corrosion during Oxide Growth Oxide Reduction and Oxidation Modification of Oxide Films by ITR of Other Ions Corrosion at Inhomogeneous Films: Breakdown, Pitting and Localized Attack Microscopic and Molecular Reasons for Local Corrosion Dielectric Breakdown Collision ionization model Tunnel model for thin films Pitting Corrosion Cathodic Breakdown Laser Induced Breakdown or Oxide Growth Applications Conclusions Acknowledgments

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The stability of the passive state of iron–chromium alloys in sulphuric acid solution

Cited by 96 publications

References 35 publications

Electrochemical corrosion behaviors and protective properties of Ni–Co–TiO₂ composite coating prepared on sintered NdFeB magnet

Electrochemical corrosion behaviors and protective properties of Ni–Co–TiO₂ composite coating prepared on sintered NdFeB magnet

Corrosão de aços inoxidáveis avançados em meios fisiológicos

Passivity of Metals, Alloys, and Semiconductors

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The stability of the passive state of iron–chromium alloys in sulphuric acid solution

Cited by 96 publications

References 35 publications

Electrochemical corrosion behaviors and protective properties of Ni–Co–TiO2 composite coating prepared on sintered NdFeB magnet

Electrochemical corrosion behaviors and protective properties of Ni–Co–TiO2 composite coating prepared on sintered NdFeB magnet

Corrosão de aços inoxidáveis avançados em meios fisiológicos

Passivity of Metals, Alloys, and Semiconductors

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Electrochemical corrosion behaviors and protective properties of Ni–Co–TiO₂ composite coating prepared on sintered NdFeB magnet

Electrochemical corrosion behaviors and protective properties of Ni–Co–TiO₂ composite coating prepared on sintered NdFeB magnet