Effects of fluoride ions in the growth of barrier-type films on aluminium

Elaish, R.; Curioni, Michele; Gowers, K. R.; Kasuga, Atsushi; Habazaki, H.; Hashimoto, Teruo; Skeldon, P.

doi:10.1016/j.electacta.2017.06.034

Cited by 18 publications

(9 citation statements)

References 35 publications

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“…8 A previous study of fluoride incorporation into barrier-type films showed that fluoride ions migrate inwards in anodic alumina at about twice the rate of O 2− ions. 23 Consequently, a fluoride-rich layer should be present next to the substrate and also along the cell boundaries in the present films, as illustrated in the schematic diagram of Figure 9. The presence of a fluoride-rich layer at the film base was found by XPS analysis of a film formed in oxalic acid with added fluoride, 9 and is suggested to be present in the films formed in sulfuric acid according to the GDOES profiles of Figure 6.…”

Section: Resultsmentioning

confidence: 95%

Influence of Fluorozirconic Acid on Sulfuric Acid Anodizing of Aluminum

Elaish¹,

Curioni

Gowers³

et al. 2017

J. Electrochem. Soc.

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The effects of additions of fluorozirconic acid to sulfuric acid on the anodizing behavior of aluminum have been investigated under a constant voltage at temperatures of 0 and 20 • C. The fluoroacid increased the rate of film growth, with a dependence on the fluoroacid concentration, the electrolyte temperature and the anodizing time. Compositional analyses showed that fluorine species were present in the films. However, zirconium species were absent. The fluoroacid generally enhanced film dissolution, although this effect was less important at low fluoroacid concentration, low electrolyte temperature and short anodizing times. Chromium (VI)-free conversion treatments that include fluorotitanic and fluorozirconic acids in the bath formulations have been developed for aluminum alloys.1-6 The resultant coatings comprise chromium (III) (if present in the bath), titanium and zirconium fluorides, oxides and hydroxides, which constitute the main part of the coating thickness, and a comparatively thin layer of aluminum oxyfluoride next to the substrate. In comparison with the findings from the relatively numerous studies of conversion coatings produced using fluoroacids, very little information is available on the use of fluoroacids in anodizing of aluminum and aluminum alloys. One study has been made of anodizing aluminum and aluminum alloys at a constant current density in fluoroboric acid solutions at temperatures ranging from 0 to 30• C. 7 Porous films were formed, with a pore size and population density that depended on the concentration and temperature of the fluoroboric acid solution and the time of anodizing. However, the information provided on the morphology and composition of the films was very limited and the role of the fluoroacid in the growth of the film was not considered. More recent studies examined the influence of ammonium hexafluorosilicate 8 and ammonium fluoride 8,9 additions to oxalic acid on the formation of porous anodic films on aluminum. The effect of hexafluorosilicate ions was more pronounced than that of fluoride ions, suggesting that Si

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Section: Resultsmentioning

confidence: 95%

Influence of Fluorozirconic Acid on Sulfuric Acid Anodizing of Aluminum

Elaish¹,

Curioni

Gowers³

et al. 2017

J. Electrochem. Soc.

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“…However, Cl – has higher discharge and activation abilities compared to O 2– . When the dense films are anodized in the ppm NH 4 Cl electrolytes, Cl – also does not stay only on the surface of the oxide films but migrates to the inside. − , Moreover, compared to O 2– , Cl – exhibits a greater migration rate under the same E . It weakens the electrostatic interaction between Al 3+ and O 2– , restraining the formation process of oxide films.…”

Section: Resultsmentioning

confidence: 99%

Effect of Chloride Ions on the Sparking Voltage of Working Electrolytes and Its Restraint Method

Wang

Zhang

et al. 2023

J. Phys. Chem. C

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As we all know, chloride ions (Cl–) are major impurities that significantly influence the lifetime and degradation of the dielectric properties of working electrolytes in aluminum electrolytic capacitors. However, the exact destructive mechanism of Cl– on the working electrolytes remains unstudied. In this work, ppm NH4Cl is added to the working electrolytes to study the formation process of dense films of anodic alumina and the sparking voltage of electrolytes. As a result, nanopores and hemispherical shapes similar to the morphologies of the porous alumina film are found in the originally dense films of anodic alumina and the sparking voltage of electrolytes also decreases. The presence of Cl– leads to the generation of electronic current (J e) and oxygen gas evolution in the anodizing process, which could decrease the sparking voltage. The oxygen bubbles inside the dense films of anodic alumina result in the generation of nanopores and hemispherical shapes within them. When 1 wt % ethylene glycol borate polyester (BPE) is added to the NH4Cl electrolytes, the morphologies of nanopores and hemispherical shapes in the dense films disappear, which proves that BPE can not only restrain the generation of J e and oxygen gas evolution but also improve the sparking voltage.

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“…The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/coatings12070908/s1, Figure S1 S1: Chemical composition measured by XPS on barrier oxide layers at 45° and 15° take-off angles, Table S2: Constraints applied for the curve fitting of the O1s and C1s photoelectron peaks as proposed by Abrahami et al, Table S3: Atomic concentration and standard deviation calculated from three independent measurements of each deconvoluted chemical state in the C1s and O1s photoelectron peaks, Table S4: Chemical composition estimated from the detailed spectra of porous anodic oxide films. References [43][44][45][46] are cited in the supplementary materials.…”

Section: Supplementary Materialsmentioning

confidence: 99%

The Role of Anodising Parameters in the Performance of Bare and Coated Aerospace Anodic Oxide Films

et al. 2022

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The anodising process parameters (voltage, temperature, and electrolyte) control the morphology and the chemical composition of the resulting anodic oxide film by altering the balance between oxide growth and oxide dissolution reactions. The porosity of the oxide film is reduced by the addition of tartaric acid to a sulfuric acid electrolyte, while anodising at elevated temperatures enhances oxide dissolution, leading to wider pores and rougher surfaces. No significant changes in the oxide chemical composition as a function of anodising parameters was found; in particular, no tartrate incorporation took place. The resistance of uncoated anodic oxide films against aggressive media and galvanic stress as a function of anodising parameters has been studied by electrochemical methods. Anodising in a mixed tartaric and sulfuric acid electrolyte improves the resistance of the anodic oxide against galvanic stress and aggressive media in comparison to sulfuric acid anodising processes. However, the corrosion protection performance of the anodic oxide films in combination with a corrosion-inhibitor loaded organic coating is not governed by the blank oxide properties but by the adhesion-enhancing morphological features formed during anodising at elevated temperatures at the oxide/coating interface.

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Effects of fluoride ions in the growth of barrier-type films on aluminium

Cited by 18 publications

References 35 publications

Influence of Fluorozirconic Acid on Sulfuric Acid Anodizing of Aluminum

Influence of Fluorozirconic Acid on Sulfuric Acid Anodizing of Aluminum

Effect of Chloride Ions on the Sparking Voltage of Working Electrolytes and Its Restraint Method

The Role of Anodising Parameters in the Performance of Bare and Coated Aerospace Anodic Oxide Films

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