Corrosion mechanism of pure aluminium in aqueous alkaline solution

Pyun, Su‐Il; Moon, Sungmo

doi:10.1007/s100080050203

Cited by 146 publications

(80 citation statements)

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“…Lithium is known for its facile intercalation with aluminum hydroxides to form a layered double hydroxide under alkaline conditions. 34 Li-ions react with the Al(OH) 4 − and the carbonate-ion to form a lithium aluminum hydroxide carbonate hydrate or layered double hydroxide (Li 2 [Al 2 (OH) 6 ] 2 .CO 3 .nH 2 O (Li-Al LDH)). Prolonged exposure under these conditions resulted in the further growth of the film, thus an increase of the OCP.…”

Section: Mechanism Of Formation-the Results Of This Investigationmentioning

confidence: 99%

“…First, there is the process of direct (anodic) dissolution of the aluminum metal and the formation of an amorphous aluminum hydroxide gel film on the aluminum substrate, and second, the process of chemical dissolution of the aluminum hydroxide gel film into the bulk solution. 4 In contrast, aluminum shows a passive behavior by the formation of a lithium containing film when exposed to alkaline lithium salt solutions. 1,5 This passive behavior was implemented by Buchheit et al with the development of a hexavalent chromium-free chemical conversion coating from alkaline lithium carbonate solutions (pH 11-13), generating lithium aluminum carbonate hydroxide hydrate (hydrotalcite) layers on aluminum alloys.…”

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confidence: 99%

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Mechanism of Passive Layer Formation on AA2024-T3 from Alkaline Lithium Carbonate Solutions in the Presence of Sodium Chloride

Visser

González-García

Mol

et al. 2018

J. Electrochem. Soc.

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This study focuses on the elucidation of the formation mechanism of passive layers on AA2024-T3 during the exposure to alkaline lithium carbonate solutions in the presence of sodium chloride. Under controlled conditions, in an electrochemical cell, a protective layer was generated comprising an amorphous inner layer and a crystalline outer-layer. In order to resolve the formation mechanism, the layers were characterized using surface analytical techniques to characterize the surface morphology, thickness and elemental composition of the layers at different stages of the formation process. In addition, electrochemical techniques were applied to link the electrochemical properties of the layers with the different stages of formation. The results demonstrate that the formation mechanism of these layers comprises three different stages: (I) oxide thinning, (II) anodic dissolution and film formation, followed by (III) film growth through a competitive growth-dissolution process. The passive properties of the layers are generated in the third stage through the densification of the amorphous layer. The combined results provide an enhanced insight in the formation mechanism and the development of the passive properties of these layers when lithium salts are used as leaching corrosion inhibitor for coated AA2024-T3. Lithium salts gained interest as corrosion inhibitor after the observations of unexpected passivity of aluminum in alkaline lithium solutions by Gui and Devine.1 Aluminum is stable in the range of pH 4 to pH 9 due to the passivity of aluminum oxide.2 However, it is known that aluminum shows a high corrosion rate at pH values higher than 10.3 The corrosion process under these alkaline conditions is dominated by two subsequent sub-processes leading to significant mass loss. First, there is the process of direct (anodic) dissolution of the aluminum metal and the formation of an amorphous aluminum hydroxide gel film on the aluminum substrate, and second, the process of chemical dissolution of the aluminum hydroxide gel film into the bulk solution.4 In contrast, aluminum shows a passive behavior by the formation of a lithium containing film when exposed to alkaline lithium salt solutions. 1,5 This passive behavior was implemented by Buchheit et al. with the development of a hexavalent chromium-free chemical conversion coating from alkaline lithium carbonate solutions (pH 11-13), generating lithium aluminum carbonate hydroxide hydrate (hydrotalcite) layers on aluminum alloys.6 They studied the composition, structure and performance of these conversion coatings in relation to processing parameters and various bath chemistries and demonstrated that these hydrotalcite coatings exhibit similar corrosion protective properties as traditional conversion coatings.7 However, application of these conversion coatings in combination with coatings did not result in an equal performance compared to hexavalent chromium-based conversion coatings. In 2010, it was discovered that lithium salts could be considered as a potential alte...

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Section: Mechanism Of Formation-the Results Of This Investigationmentioning

confidence: 99%

mentioning

confidence: 99%

Mechanism of Passive Layer Formation on AA2024-T3 from Alkaline Lithium Carbonate Solutions in the Presence of Sodium Chloride

Visser

González-García

Mol

et al. 2018

J. Electrochem. Soc.

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“…At the negative electrode the overall anodic reaction involves the oxidation of aluminium to aluminate ions [29] Al þ 4OH À / Al(OH) 4 À þ 3e À E a ¼ À2.4 V vs. Hg/HgO…”

Section: Corrosion Of 99999 Wt% High-purity Aluminium In Alkaline Somentioning

confidence: 99%

“…(13) towards the interface between the aluminium and the hydroxide film, and indirect metal dissolution reaction by consecutive film formation and dissolution [29].…”

Section: Mechanism Of Super-pure Aluminium Corrosion In Alkaline Solumentioning

confidence: 99%

“…Increasing electrolyte flow rate results in fast supply of OH À ions to the metal/solution interface and rapid removal of Al(OH) 4 À ions away from the aluminium surface, allowing more of the Al(OH) 3 layer to dissolve into the electrolyte, see Eq. (13) [29]. Among the literature, there has been no rotating disc electrode study evaluating the effect of rotation rate on the anodic and cathodic behaviour of aluminium alloys in alkaline solutions.…”

Section: Indiummentioning

confidence: 99%

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Developments in electrode materials and electrolytes for aluminium–air batteries

Egan¹,

León²,

Wood³

et al. 2013

Journal of Power Sources

402

191

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h i g h l i g h t s< Discussion of the rationale to choose a suitable alloy for Aleair battery. < Effect of the properties and preparation route to enhance the oxidation of Al. < Effect of the inhibitors on the anode oxidation in the alkaline electrolyte. This review shows the influence of the materials, including: aluminium alloy, oxygen reduction catalyst and electrolyte type, in the battery performance. Two issues are considered: (a) the parasitic corrosion of aluminium at open-circuit potential and under discharge, due to the reduction of water on the anode and (b) the formation of a passive hydroxide layer on aluminium, which inhibits dissolution and shifts its potential to positive values. To overcome these two issues, super-pure (99.999 wt%) aluminium alloyed with traces of Mg, Sn, In and Ga are used to inhibit corrosion or to break down the passive hydroxide layer. Since high-purity aluminium alloys are expensive, an alternative approach is to add inhibitors or additives directly into the electrolyte. The effectiveness of binary and ternary alloys and the addition of different electrolyte additives are evaluated. Novel methods to overcome the self-corrosion problem include using anionic membranes and gel electrolytes or alternative solvents, such as alcohols or ionic liquids, to replace aqueous solutions. The air cathode is also considered and future opportunities and directions for the development of aluminiumeair cells are highlighted.

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