Strategies for the replacement of chromic acid anodising for the structural bonding of aluminium alloys

Critchlow, Gary W.; Yendall, Keith A.; Bahrani, D.; Quinn, A. M.; Andrews, F. A.

doi:10.1016/j.ijadhadh.2005.07.001

Cited by 155 publications

(87 citation statements)

References 81 publications

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“…Increasing anodising time increases oxide film thickness, although eventually a specific thickness is reached, where, at that point, the rate of oxide formation and dissolution are in equilibrium [11,15]. Fig.…”

Section: Discussionmentioning

confidence: 99%

Optimising sulfuric acid hard coat anodising for an Al-Mg-Si wrought aluminium alloy

Bartolo

Sinagra

Mallia

2014

Materials Science-Poland

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This research evaluates the effects of sulfuric acid hard coat anodising parameters, such as acid concentration, electrolyte temperature, current density and time, on the hardness and thickness of the resultant anodised layers. A small scale anodising facility was designed and set up to enable experimental investigation of the anodising parameters. An experimental design using the Taguchi method to optimise the parameters within an established operating window was performed. Qualitative and quantitative methods of characterisation of the resultant anodised layers were carried out. The anodised layer's thickness, and morphology were determined using a light optical microscope (LOM) and field emission gun scanning electron microscope (FEG-SEM). Hardness measurements were carried out using a nano hardness tester. Correlations between the various anodising parameters and their effect on the hardness and thickness of the anodised layers were established. Careful evaluation of these effects enabled optimum parameters to be determined using the Taguchi method, which were verified experimentally. Anodised layers having hardness varying between 2.4 -5.2 GPa and a thickness of between 20 -80 µm were produced. The Taguchi method was shown to be applicable to anodising. This finding could facilitate on-going and future research and development of anodising, which is attracting remarkable academic and industrial interest.

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Section: Discussionmentioning

confidence: 99%

Optimising sulfuric acid hard coat anodising for an Al-Mg-Si wrought aluminium alloy

Bartolo

Sinagra

Mallia

2014

Materials Science-Poland

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“…4 Nevertheless, the excellent adhesion and corrosion resistance that is achieved by the complete Cr(VI)-based pre-treatment process currently applied by the European aerospace industry is not easily duplicated. 5 Since strict international environmental and health regulations announced the near future ban of Cr(VI), its replacement has become a critical and timely issue. 6 Reviewing the literature to date, the high strength of these bonded structures is attributed to the accumulated effect of two main mechanisms: (1) mechanical interlocking and (2) chemical interactions and physical interactions between the oxide and the organic resin.…”

Section: Introductionmentioning

confidence: 99%

Interface strength and degradation of adhesively bonded porous aluminum oxides

Abrahami

Kok²,

Gudla

et al. 2017

npj Mater Degrad

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For more than six decades, chromic acid anodizing has been the main step in the surface treatment of aluminum for adhesively bonded aircraft structures. Soon this process, known for producing a readily adherent oxide with an excellent corrosion resistance, will be banned by strict international environmental and health regulations. Replacing this traditional process in a high-demanding and high-risk industry such as aircraft construction requires an in-depth understanding of the underlying adhesion and degradation mechanisms at the oxide/resin interface resulting from alternative processes. The relationship between the anodizing conditions in sulfuric and mixtures of sulfuric and phosphoric acid electrolytes and the formation and durability of bonding under various environmental conditions was investigated. Scanning electron microscopy was used to characterize the oxide features. Selected specimens were studied with transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy to measure resin concentration within structurally different porous anodic oxide layers as a function of depth. Results show that there are two critical morphological aspects for strong and durable bonding. First, a minimum pore size is pivotal for the formation of a stable interface, as reflected by the initial peel strengths. Second, the increased surface roughness of the oxide/resin interface caused by extended chemical dissolution at higher temperature and higher phosphoric acid concentration is crucial to assure bond durability under water ingress. There is, however, an upper limit to the beneficial amount of anodic dissolution above which bonds are prone for corrosive degradation. Morphology is, however, not the only prerequisite for good bonding and bond performance also depends on the oxides' chemical composition.

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“…Different studies have shown that bonding performance is affected by changing the oxide morphology [10][11][12] .…”

Section: Introductionmentioning

confidence: 99%

Adhesive Bonding and Corrosion Performance Investigated as a Function of Aluminum Oxide Chemistry and Adhesives

Abrahami

Hauffman

Kok³

et al. 2017

CORROSION

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Strategies for the replacement of chromic acid anodising for the structural bonding of aluminium alloys

Cited by 155 publications

References 81 publications

Optimising sulfuric acid hard coat anodising for an Al-Mg-Si wrought aluminium alloy

Optimising sulfuric acid hard coat anodising for an Al-Mg-Si wrought aluminium alloy

Interface strength and degradation of adhesively bonded porous aluminum oxides

Adhesive Bonding and Corrosion Performance Investigated as a Function of Aluminum Oxide Chemistry and Adhesives

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