Effect of acid traces on hydrothermal sealing of anodising layers on 2024 aluminium alloy

Arenas, M.A.; Conde, A.; Damborenea, J. de

doi:10.1016/j.electacta.2010.07.089

Cited by 65 publications

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“…The role of tartaric acid on the anodizing and corrosion behavior of AA2024-T3 alloy was further investigated by Curioni et al 15 The authors concluded that the good corrosion performance of the alloy anodized in the presence of tartaric acid was due to residual tartaric acid in the pores of the anodic film. This was supported by the work of Arenas et al, 16 who found enhanced corrosion properties of anodized AA2024-T3 alloy using TSA process after hydrothermal sealing, compared with SAA process. The authors related such enhancement to the dissociation of residual tartaric acid in the pores of the anodic film and the subsequent formation of chelate complex between tartrate ions and Cu (II) cations incorporated in the oxide film.…”

supporting

confidence: 68%

“…The reason that tartaric acid suppressed the dissolution of the bulk anodic film and the anodic film formed from T 1 phase may be associated with the complexing action between anions from tartaric acid and cations from the alloy. 16 The formed complex compound was absorbed on the porous film surface, leading to reduced dissolution rate of the anodic film. The reduced dissolution of the anodic film (therefore reduced porosity) was at least partially responsible for the improved corrosion resistance of the anodic films with increasing tartaric acid concentration.…”

Section: Discussionmentioning

confidence: 99%

“…Since then, the anodization behavior of aerospace aluminum alloys based on TSA process has been increasingly investigated. [12][13][14][15][16][17][18] Iglesias-Rubianes et al 12 investigated the effect of tartaric acid addition to sulfuric acid on the anodization behavior of sputteringdeposited Al-Cu alloy and AA2024-T3 alloy. It was reported that the presence of tartaric acid did not change the film morphology, but resulted in 10-20% reduction of the anodizing rate during constant voltage anodizing.…”

mentioning

confidence: 99%

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Effect of Anodizing Parameters on Film Morphology and Corrosion Resistance of AA2099 Aluminum-Lithium Alloy

Zhou

Liao

et al. 2016

J. Electrochem. Soc.

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The effect of anodization temperature and tartaric acid concentration on the morphology and corrosion resistance of the anodic film formed on AA2099-T8 alloy in tartaric-sulfuric acid was investigated. It was found that the dissolution of the anodic film during anodizing led to increased pore size, rod-shaped cavities and grain boundary grooves in the anodic films. The rod-shaped cavities and grain boundary grooves are associated with selective dissolution of the anodic film formed from fine T 1 (Al 2 CuLi) phase precipitates due to the difference in the reactivity of the films formed from different phases. The increased porosity due to dissolution degraded the corrosion resistance of the anodic film. In the temperature range of 22-47 • C, with 0.53 M tartaric acid addition, anodizing at 42 • C provided the best corrosion performance and a relatively high anodizing efficiency; in the tartaric acid concentration range of 0-0.9 M, at 37 • C, anodizing in electrolytes containing 0.7 and 0.9 M tartaric acid provided good corrosion resistance with little decrease of anodizing efficiency. The corrosive medium did not penetrate the anodic film uniformly but preferentially at local sites, resulting in localized corrosion of the anodized alloy. Aluminum and its alloys are protected from corrosion by an airformed oxide film of several nanometers thickness. However, the protective ability of the air-formed oxide film is limited due to its small thickness. In order to obtain more reliable and durable protection for aluminum and its alloys, a relatively thick oxide film has been pursued. As a case in point, aerospace aluminum alloys are anodized in acidic electrolyte to produce a relatively thick anodic oxide film of a few micrometers, providing the alloys with reasonable corrosion resistance and/or suitable surface for painting and adhesive bonding. Chromic acid anodizing (CAA) used to be the most widely employed anodizing process in aerospace industry.1-3 However, the high toxicity associated with Cr (VI) has restricted the application of CAA. Since 1990s, there have been many efforts to find alternative anodizing process to replace CAA in aerospace industry. [4][5][6] Sulfuric acid anodizing (SAA) is a commonly used, environmentally friendly anodizing process. However, a relatively thicker anodic film is needed for SAA than for CAA if the same corrosion resistance is required. 3On the other hand, increased film thickness will sacrifice fatigue resistance of the anodized components, 3,7-9 not mentioning cost increase. In 1990, Wong et al.3 invented a boric-sulfuric acid anodizing (BSA) process, which modifies the traditional SAA process by reducing the concentration of sulfuric acid and adding boric acid. It is now recognized that the performance of the anodic film produced by BSA is similar to that of the anodic film produced by CAA. 5,10 At the begin of the twenty first century, a new anodizing process, called tartaricsulfuric acid anodizing (TSA), was patented by Alenia Aeronautica S.P.A.11 to compete with BSA. Since th...

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confidence: 68%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Effect of Anodizing Parameters on Film Morphology and Corrosion Resistance of AA2099 Aluminum-Lithium Alloy

Zhou

Liao

et al. 2016

J. Electrochem. Soc.

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“…In order to completely remove Cr(VI) from the process, anodic films produced from tartaric-sulfuric anodizing (TSA) baths have been frequently sealed by immersion in boiling water [12]. Several works have shown that hydrothermally sealed anodic films produced on 2XXX Al alloys from TSA baths have superior corrosion resistance when compared with their counterparts produced from sulfuric acid baths [12,23]. It has been suggested that residual tartaric acid left inside the pores after the anodizing process [24] may form chelates complexes with Cu(II) cations present in the anodic film reducing the heterogeneities of this latter [23].…”

mentioning

confidence: 99%

Corrosion protection of clad 2024 aluminum alloy anodized in tartaric-sulfuric acid bath and protected with hybrid sol–gel coating

Capelossi

Poelman

Recloux

et al. 2014

Electrochimica Acta

151

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“…The pore diameter, thickness, structure and morphology of the oxide layer depend on the applied anodizing conditions, such as anodizing potential, temperature and electrolyte. 2 Traditionally, anodizing of aluminum alloys is usually performed in chromic acid electrolytes, and it is followed by sealing in dichromate solution. However, as a result of its toxicity, 3 legislation will severely restrict the use of sodium dichromate, which has led to the development of alternative dichromate-free sealing treatments.…”

mentioning

confidence: 99%

Development of a Chromium-Free Post-Anodizing Treatment Based on 2-Mercaptobenzothiazole for Corrosion Protection of AA2024T3

Yang¹,

Yang²,

Balaskas³

et al. 2017

J. Electrochem. Soc.

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The anticorrosion performance provided by new anodizing and sealing methods for the AA2024T3 aluminum alloy is discussed in this work. Two anti-corrosion post-anodizing treatments based on immersion in an ethanol solution containing 2-mercapto-benzothiazole (2-MBT) were applied. Both treatments consisted of the immersion of the anodized specimens in 2-MBT ethanol solution, but the second was followed by hydrothermal sealing in water. Electrochemical Impedance Spectroscopy (EIS) and an immersion test show that both treatments exhibited improved corrosion resistance compared with anodized AA2024-T3 that was only hot water sealed. Considering that these novel anti-corrosion methods appear to provide enhanced, long-term and stable corrosion resistance to the AA2024T3 aluminum alloy, the use of 2-mercaptobenzothiazole (2-MBT) is proposed as a promising inhibitor in sealing treatments. AA2024T3 aluminum alloy is widely used in the aerospace industry due to its high strength to weight ratio.1 However, high amounts of copper, together with magnesium and other alloying elements, generate second-phase particles that cause microgalvanic coupling in the presence of moisture or aqueous electrolyte, thereby reducing corrosion resistance.Anodizing is an electrochemical method that converts the aluminum surface into a corrosion-resistant, durable oxide layer with a porous structure. The pore diameter, thickness, structure and morphology of the oxide layer depend on the applied anodizing conditions, such as anodizing potential, temperature and electrolyte.2 Traditionally, anodizing of aluminum alloys is usually performed in chromic acid electrolytes, and it is followed by sealing in dichromate solution. However, as a result of its toxicity, 3 legislation will severely restrict the use of sodium dichromate, which has led to the development of alternative dichromate-free sealing treatments. [4][5][6] The restriction on the use of chromium Cr (IV) compounds has also led to the development of alternative chromium-free anodizing methods, including the sulfuric-tartaric process (TSA), a typical anodizing method used in aerospace industries. [7][8][9][10] In simple terms, the anodizing process is used to obtain a thick aluminum oxide layer with a porous structure, whereas the sealing process is used to close the pores with hydrated products, thereby further increasing the corrosion resistance. A detailed discussion of the complex effects of pore morphology, film thickness, sealing time and nature of the sealing solution can be found elsewhere and it is not reported in detail here.11-15 Different types of sealing methods have been studied, including dichromate sealing, hot water sealing, and nickel acetate sealing. 16 Commonly quoted sealing treatments are hot water or aqueous nickel acetate, but neither is as good as hexavalent chromiumbased processes; moreover, both are energy consuming as the sealing takes place at 95• C. In addition, new sealing techniques such as cerium sealing have been developed during the last decade, 10,[17][18...

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Effect of acid traces on hydrothermal sealing of anodising layers on 2024 aluminium alloy

Cited by 65 publications

References 19 publications

Effect of Anodizing Parameters on Film Morphology and Corrosion Resistance of AA2099 Aluminum-Lithium Alloy

Effect of Anodizing Parameters on Film Morphology and Corrosion Resistance of AA2099 Aluminum-Lithium Alloy

Corrosion protection of clad 2024 aluminum alloy anodized in tartaric-sulfuric acid bath and protected with hybrid sol–gel coating

Development of a Chromium-Free Post-Anodizing Treatment Based on 2-Mercaptobenzothiazole for Corrosion Protection of AA2024T3

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