Resumen de Revestimientos a base de sílica e ácido fosfônico para proteção anticorrosiva da liga de alumínio AA2024-T3
Viviane Dalmoro
The aluminum alloy AA2024-T3, u sed extensively in the aerospace industry, dueto the heterogeneous microstructures intentionally designed to optímize the mechanical properties, is very susceptible to localized corrosion. In order to prevent the corrosion several surface treatments have been investigated to replace the chromate treatment and, in thís way, sílica based films can be regarded as a promising alternatíve. The aim ofthis work ís the obtaíníng, development and characterízation offilms vinyltrímethoxysilane (VfMS) combíned wíth tetraethylorthosílícate (TEOS) or y-glycídoxypropyltrímethoxysílane in the presence and absence of ethylenedíamíne tetrametílene phosphoníc a cid (EDTPO) as pretreatments agaínst corros ion of alumínum alloy AA2024-T3 in NaCI 0.05 mol L-1. Furthermore, ít was investígated the effect of addíng clayto sol-gel hybríd matríx and sílica nanoparticles to the matrix of VfMS/GPTMS films containing EDTPO. Different ratios of precursor and silica concentrations of phosphonic acid and elay were evaluated. The anticorrosíve properties ofthe alloycoated with the modífied sílíca films were studied using electrochemical impedance spectroscopy (El S) after different immersion times. The chemical structure ofthe films and the starting solutíons were characterízed by ínfrared spectroscopy (FT-IR), whíle the morphology and com posítion of the films were examíned on usíng Scanníng Electron Microscopy (SEM), Energy Dispersive Spectroscopy X-Ray (E O X) and 1 or Photoelectron Spectroscopy X-Ray (XPS). The results obtained were posítive for the corrosion protectíon of AA2024 using the coatings obtaíned by the sol-gel method and modífied with phosphonic acid. Meroptimization of the coatings of silica and silica/phosphonic acid we applied !he bes! systems as anticorrosíve pretreatments and adhesion promoters for one epoxy primer paínt. Accelerated corrosion tests allowed check the beneficial action of the silica layer as anchoring system for the epoxy paint. lt was found that the systems composed by: silica/epox paint and silica + phosphonic acid/epoxy paint and silica/ epoxy paint modified with conducting polymer provide effective corrosion protection for the alloy AA2024-T3. The results deríved from the present thesis have been accepted or have been sent for publicatíon in ínternational journals and also reported in sorne international congresses, as we point below: [1] V. Dalmoro, J . H. Z. dos Santos, E. Armelin, C. Alemán, O. S. Azambuja, Phosphonic acid/silica-based films: A potential treatment for corros ion protection, Corros. Sci. 60 (2012) 173-180. [2] V. Dalmoro, J. H. Z. dos Santos, E. Armelín, C. Alemán, D. S. Azambuja, A synergistic combination of tetraethylorthosilicate and multiphosphonic acid offers excellent corros ion protectíon to AA1100 aluminum alloy, Appl. Surf. Sci . 273 (2013) 758-768. [3] V. Dalmoro, J . H. Z. dos Santos, l. M. I.M. Baibich, E. Armelin, C. Alemán, O. S. Azambuja Cooperatíve effect between VfMS/TEOS and phosphonic acid for corros ion protection of AA2024, Submitted, 2013. [4] V. Dalmoro, J. H. Z. dos Santos, E. Armelín, C. Alemán, D. S. Azambuja, Organosílane and Montmorílloníte-based hybríd films produced by sol-gel: A potencial treatrnent for corros ion of AA2024, Manuscript on preparation, 2013. [5] V. Dalmoro, J. H. Z. dos Santos, E. Armelin, C. Alemán, D. S. Azambuja, Characterization fTEOS/phosphoníc acíd films, 63rd Annual Meeting of lnternatíonal Socíety of Electrochem ís try 19-24 August 2012, Prague, Chech Republíc
