Review of alternatives to chromate for corrosion protection of aluminum aerospace alloys

Twite, R.; Bierwagen, Gordon P.

doi:10.1016/s0300-9440(98)00015-0

Cited by 735 publications

(404 citation statements)

References 35 publications

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“…In the last decade, one of the biggest challenge in the field of corrosion has been the replacement of chromium based pre-treatments and primers by 'green' solutions [1].…”

Section: Introductionmentioning

confidence: 99%

Corrosion protection of AA2024 by sol–gel coatings modified with MBT-loaded polyurea microcapsules

Maia

Yasakau

Carneiro

et al. 2016

Chemical Engineering Journal

109

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In this work we report the synthesis of polyurea microcapsules loaded with corrosion inhibitor 2-mercaptobenzothiazole (MBT) for corrosion protection of 2024 aluminum alloy. The microcapsules were prepared by interfacial polycondensation. The resulting capsules exhibit spherical shape, with diameter ranging between 100 nm and 2 µm. The loading content of MBT was found to be 5 wt% and release studies showed that MBT is preferentially released under acidic and alkaline conditions and follows the Fickian diffusion model. This pH dependency seems suitable for protection of metallic alloys where corrosion processes are accompanied by local pH changes. Furthermore, the microcapsules were added to a hybrid sol-gel coating and its performance assessed by electrochemical and accelerated standard tests. The results obtained indicate that capsules loaded with MBT do not affect negatively the barrier properties of sol-gel coatings, and contribute for the enhancement of adhesion of coatings to the metallic substrate. More relevant, these additives impart active corrosion protection suppressing corrosion activity at defect sites, which opens prospects for application of polyurea microcapsules as additives for high-performance coatings.

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“…In the last decade, one of the biggest challenge in the field of corrosion has been the replacement of chromium based pre-treatments and primers by 'green' solutions [1].…”

Section: Introductionmentioning

confidence: 99%

Corrosion protection of AA2024 by sol–gel coatings modified with MBT-loaded polyurea microcapsules

Maia

Yasakau

Carneiro

et al. 2016

Chemical Engineering Journal

109

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“…However in the interest of human health [2,3] and environmental concerns, alternative solutions are being pursued. For engineering applications organic polymers (polyesters, polyamides, alkyds, and polyurethane) [4], conductive polymers (polyaniline and polypyrrole) [5] and sol-gel derived organicinorganic hybrid materials have emerged as promising Cr 6+ alternatives [6].…”

Section: Introductionmentioning

confidence: 99%

Corrosion protection of AA 2024-T3 aluminium alloys using 3, 4-diaminobenzoic acid chelated zirconium–silane hybrid sol–gels

Varma

Colreavy

Cassidy³

et al. 2010

Thin Solid Films

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Organic-inorganic polymers formed by hydrolysis/condensation reactions of alkoxide precursors, such as organically modified silanes (Ormosils) are used for several industrial applications such as electronic, optical and protective anticorrosion coatings. Such materials possess superior chemical stability, physical strength and scratch resistance characteristics when compared to organic polymers. Further performance improvement can be achieved through the incorporation of zirconium and titanium based nanoparticles, also formed through from precursors via the sol-gel process. However due to the inherent reactivity differences of the above precursors, they must be hydrolysed separately before being combined for final condensation. Zirconium precursors are commonly chelated using acetic acid or acetyl acetonate prior to hydrolysis, to lower the hydrolysis rate. In this body of work, 3,4-diaminobenzoic acid (DABA) and acetyl acetonate (acac) were compared as chelating ligands for controlling the hydrolysis reactions of zirconium n-propoxide to form nanoparticles within a silane sol matrix. The sols were applied as coatings on aerospace grade aluminium alloy AA 2024-T3 and characterised by physical, spectroscopical, microscopical, electrochemical and calorimetric techniques. The electrochemical properties of the coatings, as characterised by EIS and PDS, correlated with neutral salt spray evaluations confirming that the use of DABA as a chelating ligand significantly improved the coating performance when compared to the traditional diketone ligand. The data indicates the anticorrosion properties of the nitrogen rich chelate have a key role in protecting the alloy through the formation of smaller zirconium nanoparticles, thus improving the polymer network stability.

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“…The general approach for applying these coatings relies on metal finishing treatments (treatment prior to painting involving immersion in acidic and alkaline baths)) with the objective of reducing the heterogeneous nature of the metal surface such as removing the NSDL and second phase particles (Muster 2009). This is achieved in multistep treatment processes for metal protection (Twite and Bierwagen 1998;Muster 2009) as for instance: 1. selective deoxidation (IM particle removal and surface etching); 2. deposition or growth of a manufactured oxide via electrochemical (anodising) or chemical (conversion coating) means; 3. use of an organic coating for specific applications, normally including a primer and a top-coat. On aluminium, most anodised coating processes produce an outer oxide with a cellular structure on top of a thin barrier layer that provides some protection against corrosion.…”

Section: Corrosion and Protectionmentioning

confidence: 99%

High Strength Al-Alloys: Microstructure, Corrosion and Principles of Protection

Hughés

Birbilis

Mol³

et al. 2011

Recent Trends in Processing and Degradation of Aluminium Alloys

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Review of alternatives to chromate for corrosion protection of aluminum aerospace alloys

Cited by 735 publications

References 35 publications

Corrosion protection of AA2024 by sol–gel coatings modified with MBT-loaded polyurea microcapsules

Corrosion protection of AA2024 by sol–gel coatings modified with MBT-loaded polyurea microcapsules

Corrosion protection of AA 2024-T3 aluminium alloys using 3, 4-diaminobenzoic acid chelated zirconium–silane hybrid sol–gels

High Strength Al-Alloys: Microstructure, Corrosion and Principles of Protection

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