Growth of barrier-type anodic films on magnesium in ethylene glycol electrolytes containing fluoride and water

Habazaki, H.; Kataoka, Fumitaka; Shahzad, Khurram; Tsuji, Etsushi; Aoki, Yoshitaka; Nagata, Shinji; Skeldon, P.; Thompson, G.E.

doi:10.1016/j.electacta.2015.02.168

Cited by 7 publications

(13 citation statements)

References 47 publications

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“…The XRD patterns of the anodized specimens reveal only the re ections from the hcp magnesium lm and the fcc aluminum substrate; the absence of re ections from the anodic lms suggests that the anodic lms formed in the present electrolytes containing phosphate are amorphous. This is consistent with our previous study that lm structure becomes amorphous by the addition of phosphate in the EG electrolyte containing 0.1 mol dm −3 H 2 O and 0.1 mol dm −3 NH 4 F, 19) although crystalline MgF 2 phase was present in the anodic lm formed in the phosphate-free EG-H 2 O electrolytes containing NH 4 F.…”

Section: Structure Of Anodic Lmssupporting

confidence: 82%

“…Figure 2 shows the change in the slope of the voltage rise with the H 2 O concentration in electrolyte. The slopes obtained in the phosphate-free EG-H 2 O electrolytes with the same uoride concentration 19) are also included in this gure. The slopes are always lower in the phosphate-containing electrolytes ( 0.76 V s ).…”

Section: Methodsmentioning

confidence: 99%

“…A transmission electron micrograph of the anodic lm formed to 200 V in the phosphate-containing EG-H 2 O electrolyte with 0.18 vol% H 2 O, reported previously, 19) disclosed a uniform barrier layer of 360 nm thickness, corresponding to the formation ratio of 1.80 nm V −1…”

Section: Structure Of Anodic Lmsmentioning

confidence: 99%

“…18) In uence of phosphate addition into the uoride/EG electrolytes on the growth, structure and composition of the anodic lms was also investigated. 19) The incorporation of phosphate changed the lm structure from crystalline to amorphous. In addition, much thicker anodic lms were formed at the same formation voltage in the phosphate-containing electrolyte, indicating the increase of the PBR value by phosphate incorporation.…”

Section: Introductionmentioning

confidence: 99%

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Growth of Barrier Type Anodic Film on Magnesium in Ethylene Glycol-Water Mixed Electrolytes Containing Fluoride and Phosphate

et al. 2016

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In this study, we report the formation of barrier-type anodic lms on magnetron-sputtered magnesium lms at a constant current density of 10 A m −2 in ethylene glycol (EG)-H 2 O electrolytes containing 0.1 mol dm −3 ammonium uoride and 0.1 mol dm −3 dipotassium hydrogen phosphate. The growth ef ciency is close to 100% up to 10 vol% H 2 O, but decreases to 52% in the EG-free aqueous electrolyte. Even at such a low ef ciency in the aqueous electrolyte a uniform barrier-type anodic lm with at and parallel metal/ lm and lm/electrolyte interfaces is developed over 100 V. This is contrast to the non-uniform lm growth and low breakdown voltage in the phosphate-free aqueous electrolyte containing ammonium uoride. The anodic lms appear to be amorphous regardless of H 2 O concentration in the phosphate-containing electrolytes, and consist of phosphate-incorporated oxy uoride. The phosphate incorporation is suppressed by an increase in H 2 O concentration. In addition, the anodic lms consist of two layers with an inner layer containing less amount of phosphate. The outer layer is probably formed at the lm/electrolyte interface by the migration of Mg 2+ ions outwards, while the inner layer is formed at the metal/ lm interface. The lm formation at the former interface even in the aqueous electrolyte at low ef ciency is likely to contribute to the formation of barrier lms, not porous anodic lms.

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Section: Structure Of Anodic Lmssupporting

confidence: 82%

Section: Methodsmentioning

confidence: 99%

Section: Structure Of Anodic Lmsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Growth of Barrier Type Anodic Film on Magnesium in Ethylene Glycol-Water Mixed Electrolytes Containing Fluoride and Phosphate

et al. 2016

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“…In this respect, it has recently been found that gold is oxidized during formation of fluoride-rich films on an Mg-Au substrate and gold species migrate outward at ∼0.4 times the rate of migration of magnesium. 31 Further, the migrating species appear to be associated with fluorine. In contrast, for Al-Au alloys, gold is incorporated into oxide films as metal nanoparticles.…”

mentioning

confidence: 99%

Behavior of Alloying Elements during Anodizing of Mg-Cu and Mg-W Alloys in a Fluoride/Glycerol Electrolyte

Palagonia

Němcová

Kuběna

et al. 2015

J. Electrochem. Soc.

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Anodizing of sputtering-deposited magnesium and Mg-0.75at.%Cu and Mg-1.23at.%W alloys has been carried out in a fluoride/glycerol electrolyte. The aims of the study were to investigate the enrichment of alloying elements in the alloy immediately beneath the anodic film and the migration of alloying element species in the film. The specimens were examined by electron microscopy and ion beam analysis. An enrichment of copper is revealed in the Mg-Cu alloy that increases with the anodizing time up to ∼6×10 15 Cu atoms cm −2 . Copper species are then incorporated into the anodic film and migrate outwards. In contrast, no enrichment of tungsten occurs in the Mg-W alloy, and tungsten species are immobile in the film. Anodizing treatments have long been used for the protection of magnesium alloys against corrosion and wear and interest still remains in improving and extending the range of available technologies. [1][2][3][4][5][6] Nevertheless, fundamental knowledge of anodizing of magnesium, 7 for instance relating to the migration rates and transport numbers of film species, is comparatively limited, in part due to the difficulty of forming films of uniform composition and thickness, and also to their reactivity to water. The formation of barrier-type anodic films has been extensively investigated on the valve metals, especially for aluminum, niobium, tantalum, titanium and zirconium.8 These studies have shown that oxide films of uniform thickness are formed under a high electric field that depends upon the film composition and the rate of film growth. [8][9][10] The films on aluminum, tantalum and niobium are usually amorphous, 8 and their formation involves migration of metal ions and oxygen ions, with significant contributions of both types, e.g. the transport numbers of Al 3+ , Nb 5+ and Ta 5+ are ∼0.40, 0.24 and 0.24 respectively. 8 Further, an outer region of the oxide films often contains a low concentration of species derived from the anions of the electrolyte.11 In contrast, the films on zirconium are usually nanocrystalline and form mainly by migration of O 2− ions, 12,13 while films on titanium undergo a transition from amorphous oxide to a mixture of amorphous and crystalline oxide.14 Barrier-type films can also be formed on magnesium, although such films have received much less attention and, consequently, less is known of the details of their composition, structure and growth mechanism. Films formed in aqueous electrolytes are often reported to consist of MgF 2 , MgO and/or Mg(OH) 2 . 5,7,[15][16][17] Barrier-type films can also be formed using non-aqueous electrolytes and the formation of uniform films in such electrolytes provides the opportunity for systematic studies of the anodizing behavior. 18,19 From previous work, anodizing of magnesium alloys can result in the enrichment of alloying elements beneath the anodic film. Such enrichments have been reported for copper, tungsten and zinc beneath oxide/hydroxide films formed on model alloys in an aqueous electrolyte 20,21 and of zinc beneath fluoride-...

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Formation of quasi-spherical Au48-198 clusters in anodic titania nanotubes grown on Ti-Au alloys

Sepúlveda

Castaño

Echeverría

et al. 2020

Electrochemistry Communications

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Growth of barrier-type anodic films on magnesium in ethylene glycol electrolytes containing fluoride and water

Cited by 7 publications

References 47 publications

Growth of Barrier Type Anodic Film on Magnesium in Ethylene Glycol-Water Mixed Electrolytes Containing Fluoride and Phosphate

Growth of Barrier Type Anodic Film on Magnesium in Ethylene Glycol-Water Mixed Electrolytes Containing Fluoride and Phosphate

Behavior of Alloying Elements during Anodizing of Mg-Cu and Mg-W Alloys in a Fluoride/Glycerol Electrolyte

Formation of quasi-spherical Au48-198 clusters in anodic titania nanotubes grown on Ti-Au alloys

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