Reaction of porous anodic oxide films on aluminum with hot water. V Effects of additives in hot water on the hydration behavior.

満, 甲田; 英明, 高橋; 政一, 永山

doi:10.4139/sfj1950.36.27

Cited by 5 publications

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“…Takahashi et al reported that the addition of phosphate into boiling water leads to remarkable suppression of hydration of the porous alumina formed by anodizing in oxalic acid due to the formation of a complex. 52 Because the outer layer of the Eti-PA contains etidronic acid anions with two phosphonate groups in its chemical structure, similar suppression behavior may occur during immersion in boiling water. In fact, when the Eti-PA film without etidronic acid anions formed by pore widening was immersed in boiling water for 20 min, the pores were rapidly sealed by hydroxide formation (Figure 9).…”

Section: Corrosion-resistance Behavior Of Porous Alumina In a Concent...mentioning

confidence: 99%

Corrosion-Resistant Porous Alumina Formed via Anodizing Aluminum in Etidronic Acid and Its Pore-Sealing Behavior in Boiling Water

Suzuki

Kawahara

Kikuchi

et al. 2019

J. Electrochem. Soc.

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Alkaline corrosion-resistant porous alumina was fabricated by anodizing aluminum in etidronic acid, and its hydration behavior during pore sealing in boiling water was investigated. High-purity aluminum plates were anodized in sulfuric, oxalic, citric, and etidronic acid solutions. Anodizing with etidronic acid caused stable growth of a uniform, porous alumina layer at a high voltage of approximately 200 V. This porous alumina possessed a thick barrier layer with an inner layer of pure aluminum oxide and exhibited a 10-fold increase in the corrosion resistance in a 2.5 M sodium hydroxide solution. When the porous alumina film formed by sulfuric acid anodizing was immersed in boiling water, plate-like hydroxide scales rapidly formed on the whole surface, and the pores were sealed within 10 min. In the case of etidronic acid, the hydroxides formed at the bottom of the pores in the initial stage of immersion, and the thickness of the hydroxide layer gradually increased with the immersion time. The porous layer was completely sealed by long-term immersion. Although the barrier layer was reduced to approximately 80% of its original size due to hydration, a thick barrier layer was still maintained at the bottom of the pores after immersion.

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Section: Corrosion-resistance Behavior Of Porous Alumina In a Concent...mentioning

confidence: 99%

Corrosion-Resistant Porous Alumina Formed via Anodizing Aluminum in Etidronic Acid and Its Pore-Sealing Behavior in Boiling Water

Suzuki

Kawahara

Kikuchi

et al. 2019

J. Electrochem. Soc.

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“…These cells are self-ordered by anodizing under appropriate electrochemical conditions, especially under a high electric field [3,4]. When anodic porous alumina is immersed in boiling distilled water after anodizing, the nanopores are filled by hydroxide (pore-sealing) [5,6]. The sealing process causes the formation of a highly crystalline hydroxide layer on the surface of the anodic oxide, and the hydroxide layer is highly dissolution-resistant in acidic and alkaline solutions.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of anodic porous alumina via anodizing in cyclic oxocarbon acids

Kikuchi

Nakajima

Kawashima

et al. 2014

Applied Surface Science

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The growth behavior of anodic porous alumina formed by anodizing in novel electrolyte solutions, the cyclic oxocarbon acids croconic and rhodizonic acid, was investigated for the first time. High-purity aluminum specimens were anodized in 0.1 M croconic and rhodizonic acid solutions at various constant current densities. An anodic porous alumina film with a cell size of 200-450 nm grew uniformly on an aluminum substrate by rhodizonic acid anodizing at 5-40 Am -2 , and a black, burned oxide was formed at higher current density. The cell size of the porous alumina increased with current density and corresponding anodizing voltage. Anodizing in croconic acid at 293 K caused the formation of thin anodic porous alumina films as well as black, thick burned oxides. The uniformity of the porous alumina improved by increasing the temperature of the croconic acid solution, and anodic porous alumina films with a uniform film thickness were successfully obtained. Our experimental results showed that the cyclic oxocarbon acids croconic and rhodizonic acid could be employed as a suitable electrolyte for the formation of anodic porous alumina films.Key words: Aluminum; Anodizing; Anodic Porous Alumina; Croconic Acid; Rhodizonic Acid IntroductionThe anodizing of aluminum in several different acidic solutions causes the formation of anodic porous alumina (i.e., porous anodic oxide film) with characteristic nanofeatures on aluminum substrates. Porous alumina consists of nano-scale hexagonal cells perpendicular to the substrate, and each cell possesses a nanopore at its center [1,2]. These cells are self-ordered by anodizing under appropriate electrochemical conditions, especially under a high electric field [3,4]. When anodic porous alumina is immersed in boiling distilled water after anodizing, the nanopores are filled by hydroxide (pore-sealing) [5,6]. The sealing process causes the formation of a highly crystalline hydroxide layer on the surface of the anodic oxide, and the hydroxide layer is highly dissolution-resistant in acidic and alkaline solutions. Using these characteristic structural and chemical properties, anodic porous alumina has been widely investigated for many applications: antireflection structures [7,8] [50] acid have been reported to date for the fabrication of anodic porous alumina. Oxalic and malonic acid anodizing have been reported to give rise to self-ordering behavior under suitable anodizing conditions. The organic and inorganic electrolytes used to fabricate anodic porous alumina possess low dissociation constant (pKa) in aqueous solution, except for glycolic and formic acid, are diacids or triacids. However, glycolic and formic acid form dimers via hydrogen bonding in aqueous solution and may behave like diacids [52,53]. The nanofeatures of anodic porous alumina, including cell size (i.e., interpore distance) and pore diameter, are limited by these electrolytes during anodizing. Therefore, the discovery of additional electrolytes is very important in expanding the applicability of porous alum...

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“…During pore sealing, hydroxides are formed in pits and cavities in anodic oxide films, in addition to nano-pores. Assuming the density of anodic oxide films and hydroxide formed to be 3.0 and 2.4, and the chemical composition of the oxide film and the hydroxide to be Al 2 O 3 and Al 2 O 3 ·2H 2 O, the hydration causes a volume expansion of about 8% (=(2.4 × 138)/(3.0 × 102) − 1) [ 21 ]. Thus, the formation of hydroxides in pits and cavities may cause a compressive stress from inside to outside ( Figure 13 b, left), leading to cracking in the oxide film ( Figure 13 b, right).…”

Section: Discussionmentioning

confidence: 99%

“…Pore sealing is generally carried out by immersion in boiling water [ 21 ], and recently the mechanism of the hot water sealing was reviewed in detail by S. Ono et al [ 22 ]. At the initial stage of pore sealing, anodic oxide films dissolve in nano-pores to precipitated flaky aluminum hydroxides on the inner wall of pores.…”

Section: Introductionmentioning

confidence: 99%

“…The chemical reaction during pore sealing in hot water is expressed in Equation (1) [ 23 , 24 , 25 , 26 ]. Al 2 O 3 + (1 + 2x)H 2 O→2AlOOH·xH 2 O M. Kohda et al [ 21 ] determined the value of x by gravimetry and obtained x = 1–2. S. Ono et al [ 22 ] expected the x-value to be x = 0.3–1.3 and obtained a boehmite-like electron diffraction ring from the outermost layer, formed by pore sealing.…”

Section: Introductionmentioning

confidence: 99%

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Changes in the Structure and Corrosion Protection Ability of Porous Anodic Oxide Films on Pure Al and Al Alloys by Pore Sealing Treatment

et al. 2022

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It is well known that corrosion protection of pure Al is enormously improved by the formation of porous anodic oxide films and by pore sealing treatment. However, the effects of anodizing and pore sealing on corrosion protection for Al alloys are unclear, because the alloying elements included in Al alloys affect the structure of anodic oxide films. In the present study, porous anodic oxide films are formed on pure Al, 1050-, 3003- and 5052-Al alloys, and pore sealing was carried out in boiling water. Changes in the structure and corrosion protection ability of porous anodic oxide films on pure Al and the Al alloys by pore sealing, were examined by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). SEM observation showed that anodic oxide films formed on pure Al have a smooth surface after pore sealing, and that cracks are formed in anodic oxide films on 1050-, 3003- and 5052-aluminum alloys, after pore sealing. Corrosion protection after pore sealing increased with anodizing time on pure Al, but only slightly increased with anodizing time on the Al alloys.

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Reaction of porous anodic oxide films on aluminum with hot water. V Effects of additives in hot water on the hydration behavior.

Cited by 5 publications

References 0 publications

Corrosion-Resistant Porous Alumina Formed via Anodizing Aluminum in Etidronic Acid and Its Pore-Sealing Behavior in Boiling Water

Corrosion-Resistant Porous Alumina Formed via Anodizing Aluminum in Etidronic Acid and Its Pore-Sealing Behavior in Boiling Water

Fabrication of anodic porous alumina via anodizing in cyclic oxocarbon acids

Changes in the Structure and Corrosion Protection Ability of Porous Anodic Oxide Films on Pure Al and Al Alloys by Pore Sealing Treatment

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