A comparative electrochemical and ellipsometric study of the iron electrodes in different alkaline electrolytes

Albani, Oscar Alfredo; Zerbino, J. O.; Vilche, J. R.; Arvía, Alejandro Jorge

doi:10.1016/0013-4686(86)87052-9

Cited by 73 publications

(63 citation statements)

References 32 publications

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“…[34][35][36] Calcium ions can be incorporated in the outer atom layers of the inner layer and increase the protective ability of the product layers when no chlorides are present. 36 Such a case is relevant to the noncorroding specimen R. In the presence of chlorides, as in corroding specimens 3 and protected specimens 6 and 7 ͑both CP regimes were applied 120 days after conditioning in SSC͒, the film thickness increases but the protective abilities decrease.…”

Section: P57mentioning

confidence: 99%

Investigation of Corrosion and Cathodic Protection in Reinforced Concrete

Koleva¹,

Wit

Breugel³

et al. 2007

J. Electrochem. Soc.

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The electrochemical behavior of steel reinforcement in conditions of corrosion and cathodic protection was studied, using electrochemical impedance spectroscopy ͑EIS͒ and compared to reference ͑noncorroding͒ conditions. Polarization resistance ͑PR͒ method and potentiodynamic polarization ͑PDP͒ were employed as well, in addition to ac 2 pin electrical resistance monitoring, thus deriving a comparison of the involved parameters, mainly polarization resistance and bulk electrical properties, obtained by all methods. It was found out that EIS is readily applicable for evaluating electrochemical behavior of the steel surface not only for corroding or passive state, but also in conditions of cathodic protection, although the interpretation of derived parameters is not straightforward and is related to the properties of the product layers, formed on the steel surface in the different conditions. For verification of the latter dependence, EIS, PDP, and PR measurements were performed additionally in cement extract solution, using steel samples from the previously embedded rebars in all technical conditions. The bulk matrix properties in passive, corroding, or under-protection conditions can be well defined by EIS. The evaluation of the electrochemical behavior of the steel surface, in terms of deriving polarization resistance, should take into account the crystallinity, morphology, and composition of the surface layers, which were investigated by scanning electron microscopy and energy dispersive X-ray analysis. In nondamaged reinforced concrete, steel remains passive due to the high alkalinity of the concrete pore solution ͑pH 12.5-13.5͒. If damages of the concrete cover and the concrete bulk matrix occur, depending on the aggressiveness of the environment, corrosion of the steel reinforcement will be initiated. The initiation and further evolution of the corrosion process will depend on the concrete pore network permeability and connectivity on one hand and the rate of penetration, amounts and concentration of aggressive substances in the environment ͑CO 2 , chlorides, sulfates͒ on the other. In the presence of chlorides, localized corrosion takes place as a consequence of passive layer breakdown. The rate of the process depends to a significant extent on the initial surface state of the steel surface, the chloride concentration, the chloride binding capacity of the bulk concrete matrix, etc. The chloride-induced corrosion process on steel reinforcement has been largely studied in concrete and in simulated pore solutions as well.1-21 Along with the localized corrosion on the steel surface, physico-chemical and structural transformations are taking place on the steel/cement paste interface. Further, the morphological alterations and certain distribution of product layers are influencing the mechanical properties of the reinforced concrete system as a whole.Impressed current cathodic protection ͑ICCP͒ is one of the protection techniques applied to such systems. Along with minimizing the corrosion process and preventing f...

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Section: P57mentioning

confidence: 99%

Investigation of Corrosion and Cathodic Protection in Reinforced Concrete

Koleva¹,

Wit

Breugel³

et al. 2007

J. Electrochem. Soc.

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“…In the simplest case, a two layer structure of the film can be assumed, where the inner layer, ascribed as Fe 3 O 4 , acts as a barrier layer, strongly adhering to the steel surface and limiting further film growth. 3 Passivity though, is assigned to the outer, gelatinous type layer, composed of outer hydrous Fe 2 O 3 . The protective layer is additionally supported by the presence of a Ca-rich outer layer, which adheres to the steel as well.…”

Section: ͓2͔mentioning

confidence: 99%

“…According to some researchers, the calcium rich layer provides only limited protection, the inner ͑two layer͒ film of iron oxide/hydroxides is the one passivating the steel. 4 Other investigations 3,5 attribute increased protective ability of the passive layers to incorporated Ca͑OH͒ 2 in the outer atom layers of the inner passivating film. The mechanism is denoted to adsorption of Ca 2+ ions in the inner film of iron oxide/hydroxides.…”

Section: ͓2͔mentioning

confidence: 99%

Investigation of Corrosion and Cathodic Protection in Reinforced Concrete

Koleva¹,

Wit

Breugel³

et al. 2007

J. Electrochem. Soc.

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The present study explores the formation of corrosion products on the steel surface ͑using as-received low carbon construction steel͒ in reinforced concrete in conditions of corrosion and subsequent transformation of these layers in conditions of cathodic protection ͑CP͒. Of particular interest was to investigate whether the introduced pulse CP ͑a cost-effective alternative to CP͒ will lead to similar or even more favorable conversion of the product layers on the steel surface, compared to conventional techniques. Qualification and quantification of the studied layers was performed using X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive analysis, visualization of morphology and products distribution was achieved using environmental scanning electron microscopy. The steel surface was found to be covered by a layered, nonhomogeneous formation of products, differing in crystallinity and composition, comprising an inner layer, similar to Fe 3 O 4 , and an outer layer, composed of iron ͑oxy͒hydroxides and iron ͑oxy͒hydroxy-chlorides ͓i.e., a combination of ␣-, ␤, ␥-FeOOH, Fe͑O,OH,Cl͒, and Fe 2 O 3 ͔. The product layer in corroding specimens is a combination of low valent oxides and iron-oxy͑hydroxy͒chlorides, exhibiting a relatively rough morphology. The product layers in the protected specimens were far more compact. Cathodic protection reduces salinity around the steel bars, hence the inner product layer ͑mostly Fe 3 O 4 ͒ remains more uniform, whereas the outer layer exhibits reduced crystallinity. The favorable transformation phenomena were found to be more apparent under pulse CP conditions, attributed to the obviously beneficial effects of pulse CP in terms of enhanced chloride withdrawal from the steel surface and minor influence ͑less side effects͒ on the bulk concrete microstructure. The most common and important causes for reinforcement corrosion are either localized depassivation of the steel surface due to chloride ingress or more uniform corrosion due to acidification of the pore solution as result of carbonation of the cement paste. Cathodic protection ͑CP͒ has been found to be one of the most useful techniques for inhibiting chloride-induced corrosion in reinforced concrete.1 The fundamental mechanisms underlying the efficiency of CP techniques are strongly correlated to the morphology and transformations of product layers on the steel surface. The steel reinforcement used in the present study was as-received construction steel FeB500HKN ͑rebars, d = 12 mm, C Ͻ 0.22 wt %. Electrochemical impedance spectroscopy ͑EIS͒, polarizations resistance ͑PR͒ method, and potentio-dynamic polarization ͑PDP͒ were used for a comparative analysis of electrochemical parameters and corrosion behavior of the embedded steel in the reinforced concrete specimens presented here, in the relevant conditions of corrosion and CP, and the outcomes were reported previously.2 This paper pursues exploration of the formation, distribution, and morphological alterations of corrosion products in the reinforced c...

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“…The strong voltage-induced ∆J S is consistent with a reversible reduction to ferromagnetic metallic Fe at −1.26 V and oxidation to a non-or weakly magnetic oxide film at −0.18 V in 1M KOH. 41,42 Thus, when first polarizing the films at −1.26 V, electroreduction of the Fe-O layer to metallic Fe explains the large increase of J S in comparison to the as deposited state. During the subsequent oxidation step at −0.18 V, the significant decrease of J S is consistent with the expected formation of a passivating Fe-O layer composed of a mixture of Fe 3 O 4 , Fe 2 O 3 , and FeOOH.…”

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confidence: 99%

Research Update: Magnetoionic control of magnetization and anisotropy in layered oxide/metal heterostructures

et al. 2016

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Electric field control of magnetization and anisotropy in layered structures with perpendicular magnetic anisotropy is expected to increase the versatility of spintronic devices. As a model system for reversible voltage induced changes of magnetism by magnetoionic effects, we present several oxide/metal heterostructures polarized in an electrolyte. Room temperature magnetization of Fe-O/Fe layers can be changed by 64% when applying only a few volts in 1M KOH. In a next step, the bottom interface of the in-plane magnetized Fe layer is functionalized by an L10 FePt(001) underlayer exhibiting perpendicular magnetic anisotropy. During subsequent electrocrystallization and electrooxidation, well defined epitaxial Fe3O4/Fe/FePt heterostructures evolve. The application of different voltages leads to a thickness change of the Fe layer sandwiched between Fe-O and FePt. At the point of transition between rigid magnet and exchange spring magnet regime for the Fe/FePt bilayer, this induces a large variation of magnetic anisotropy.

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A comparative electrochemical and ellipsometric study of the iron electrodes in different alkaline electrolytes

Cited by 73 publications

References 32 publications

Investigation of Corrosion and Cathodic Protection in Reinforced Concrete

Investigation of Corrosion and Cathodic Protection in Reinforced Concrete

Investigation of Corrosion and Cathodic Protection in Reinforced Concrete

Research Update: Magnetoionic control of magnetization and anisotropy in layered oxide/metal heterostructures

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