Transpassivity mechanism of iron–chromium–molybdenum alloys studied by AC impedance, DC resistance and RRDE measurements

Bojinov, Martin; Fabricius, Gunilla; Laitinen, Timo; Saario, Timo

doi:10.1016/s0013-4686(99)00149-8

Cited by 50 publications

(54 citation statements)

References 29 publications

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“…The interface becomes active due to the charge transfer and the two different adsorption processes occurring at the interface. The appearance of an inductive loop at low frequencies at the transpassive potential range of some metals in acidic solutions has been reported previously [9][10][11][12][13][14][15][16].…”

Section: Resultssupporting

confidence: 68%

“…At potentials of 1.15 and 1.25 V versus SCE, it is clear that two positive inductive loops are formed. The capacitive loop appearing at high to medium frequencies is attributable to the parallel combination of the charge-transfer resistance and interfacial capacitance; the inductive loop at low frequencies reflects the relaxation of the surface coverage of an intermediate adsorption reaction [11][12][13][14][15][16]. In this study, we found that two lowfrequency inductive loops exist, indicating the adsorption of two intermediates.…”

Section: Discussionmentioning

confidence: 52%

“…The Fe concentration on the film decreases from 17 wt% at 0.8 V versus SCE (a passive potential range) to 9 wt% at 1.05 V versus SCE (a transpassive potential range). The transpassive dissolution of Cr can be regarded as a two-step reaction with an adsorbed intermediate [4,[11][12][13][14]16] taking place at the Cr positions in the outermost cation layer. This reaction occurs at an intermediate step during the transformation from Cr Cr 3+ to Cr aq 6+ , as proposed in the literature (reactions 3a and 3b) [4].…”

Section: Discussionmentioning

confidence: 99%

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Transpassivity characterization of the alloy UNS N08367 in a chloride-containing solution

Karayan

Maya-Visuet

Castaneda

2014

J Solid State Electrochem

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We investigate the transpassivity of superaustenitic stainless steel UNS N08367 in 2.5 M LiCl solution by using cyclic potentiodynamic polarization (CPP), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). The CPP curve exhibits negative hysteresis, which indicates a transpassive dissolution process instead of pitting corrosion. The transition from the passive region to the transpassive region is characterized by EIS and equivalent circuit analysis. During the transpassive dissolution of the N08367 alloy, two reactions of adsorbed intermediates are dominant, as indicated by the two inductive loops at the transpassive region. The first inductive loop is associated with the faster reaction, i.e., the adsorption of Fe intermediates. This fast reaction is significantly influenced by the preferential dissolution of Fe during the transpassive dissolution. The second inductive loop is correlated with the adsorption of the Cr intermediate. In contrast to Fe, the Cr content on the surface increases in the transpassive region compared with the content in the passive region. The XPS spectra support the time and frequency domain approach for the preferential dissolution, and the dominant species resulted from the interfacial processes at the transpassive region.

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Section: Resultssupporting

confidence: 68%

Section: Discussionmentioning

confidence: 52%

Section: Discussionmentioning

confidence: 99%

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Transpassivity characterization of the alloy UNS N08367 in a chloride-containing solution

Karayan

Maya-Visuet

Castaneda

2014

J Solid State Electrochem

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“…The transition is similar to transpassivity and indicates domination of passive film dissolution over growth. This behaviour can be attributed to stoichiometric changes of Cr(III) to Cr(VI) [48], Ni(II) to Ni(III) [49] and a catalytic effect of Mo at high potentials [50], impeding the protective behaviour of the passive film.…”

Section: Corrosion-only Potentiodynamic Polarizationmentioning

confidence: 99%

New Experimental Rig to Investigate Abrasive–Corrosive Characteristics of Metals in Aqueous Media

Salasi

Stachowiak

2010

Tribol Lett

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A new tribometer to investigate a conjoint effect of three-body abrasion and corrosion has been developed. In this design, a flat wear sample is loaded against a rotating cylindrical disc counterface and the abrasive slurry is delivered to the contact interface. Capabilities of the newly developed tribometer have been assessed through conducting abrasion-corrosion tests involving simultaneous electrochemical measurements. In this work, the stability of the passive layer on stainless steel under three-body abrasive wear in a near neutral electrolyte was investigated using potentiodynamic polarization tests. 316L Stainless Steel wear samples were abraded by coarse garnet particles in an aerated sodium sulphate electrolyte. The effects of load and speed on the polarization curves and passivity of 316L steel were determined. It was found that under abrasion-corrosion conditions 316L steel became more thermodynamically active and the passive corrosion rate has increased. Increasing the contact load resulted in a small increase in the passive corrosion current, while increasing the rotating speed had the opposite effect of decreasing the current. Linear polarization resistance method was used to analyse corrosion current changes with time during abrasion-corrosion testing. The existence of three distinct stages was explained by the third-body effect on the corrosion potential and current. First stage was revealed by continuous decrease of corrosion potential. Then, the potential reached a plateau for the second and third stages. In the first and second stages, particle constraint in the contact zone plays the major role and a linear rise in corrosion current with time has been recorded. After a certain amount of surface roughening, no further increase in particles entrapment is expected. Therefore, in the third stage steady-state corrosion current values are anticipated. The rig developed can also be used to simulate two-body abrasion-corrosion. The capabilities of the new rig have been compared against other experimental set-ups used in studies of combined abrasion-corrosion behaviour.

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“…En aquellas muestras donde el contenido de Mo es mayor, C y F, se advertiría que el aumento de corriente es mayor, esto podría deberse a que más allá de que el Mo dentro de la región pasiva contribuye beneficiosamente a la misma, cuando llegamos a la región transpasiva la cantidad de Cr(VI) liberado de las aleaciones aumenta con la adición de Mo [11], si bien la presencia y naturaleza de Mo en la película pasiva es aún profundamente debatido y, por lo tanto, la explicación para el efecto de Mo en la resistencia a la corrosión general de aceros inoxidables es, por el momento, un tema de discusión [12].…”

Section: Probeta C Siunclassified

Pasividad en solución de fosfato de aceros inoxidables solidificados unidireccionalmente

et al. 2015

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RESUMENLa pasividad de los aceros inoxidables es atribuida a la formación de una película protectora, conformada por óxidos, sobre la superficie del metal. Esta película posee propiedades semiconductoras y está relacionada con múltiples factores que la hacen de importancia para la comprensión de los fenómenos de corrosión. En este trabajo se estudia la película pasiva formada en aceros inoxidables solidificados unidireccionalmente, Fe18Cr-10Ni-2Mo-0,08C (muestra A), Fe-18Cr-14Ni-8Mo-0,03C (muestra C) y Fe-18Cr-10Ni-8Mo-0,08C (muestra F), para determinar la influencia de la variación de la estructura (equiaxial, columnar y con transición de columnar a equiaxial-TCE) en la resistencia a la corrosión, así como investigar la relación entre la resistencia a la corrosión y el espaciamiento dendrítico secundario del material. Para ello se emplean técnicas potenciodinámicas y galvanostáticas, análisis de MottSchottky y espectroscopía de impedancia electroquímica que se realizaron en solución de Na 2 HPO 4 0,5 M (pH 9,2).Las curvas potenciodinámicas indican una región pasiva y un máximo de corriente en la región transpasiva. Las medidas galvanostáticas realizadas sobre películas pasivas formadas previamente indican dos amesetamientos de potencial, debido al óxido de Cr y óxido de Fe, del cual surgen dos tiempos de transición. El mayor espesor de óxido de hierro se encuentra en las estructuras equiaxial de la muestra F, que posee el menor espaciamiento dendrítico respecto de los otras dos muestras teniendo en cuenta la misma estructura. El análisis de Mott Schottky muestra que la película pasiva se comporta como un semiconductor tipo n en el rango de potenciales de -0,45 V a 0 V, con una densidad de donores que varía de acuerdo a la composición del acero inoxidable. También se observa que la densidad de donores varía de acuerdo al tipo de estructura para un mismo material.Palabras Clave: aceros inoxidables, película pasiva, Mott Schottky, resistencia a la corrosión. ABSTRACTPassivity of the stainless steel is attributed to the development of a protector film, formed by oxides on the metal surface. This film has semiconductor properties, and it is important for the understanding of corrosion phenomena.The objective of this work is to study the passive films formed in stainless steels samples solidified unidirectionally. The composition of the alloying elements in the samples are Fe-18Cr-10Ni-2Mo-0,08C (sample A), Fe-18Cr-14Ni-8Mo-0,03C (sample C) y Fe-18Cr-10Ni-8Mo-0,08C (sample F), and determine the influence of the structure (equiaxed, columnar and columnar-to-equiaxed transition, CET) in the corrosion resistance, as well as investigate the relationship between the corrosion resistance and the size of the secondary dendritic arm spacing. For this are used potentiodynamic and galvanostatic techniques, Mott Schottky analysis and electrochemical impedance spectroscopy.The measurements were performed in Na 2 HPO 4 0,5 M (pH = 9,2), at room temperature (25ºC).Potentiodynamic measurements indicate a passive region and a maximu...

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Transpassivity mechanism of iron–chromium–molybdenum alloys studied by AC impedance, DC resistance and RRDE measurements

Cited by 50 publications

References 29 publications

Transpassivity characterization of the alloy UNS N08367 in a chloride-containing solution

Transpassivity characterization of the alloy UNS N08367 in a chloride-containing solution

New Experimental Rig to Investigate Abrasive–Corrosive Characteristics of Metals in Aqueous Media

Pasividad en solución de fosfato de aceros inoxidables solidificados unidireccionalmente

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