Limitations of organicinorganic hybrid solgel

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Limitations of organic–inorganic hybrid sol–gel coatings for corrosion protection In the last two decades, the existing knowledge about sol–gel processing and relations between structure and properties has had an exceptional development. Con- sequently, the research efforts on this particular area of materials science have grown, allowing scientists to gain knowledge on how to develop new OIH gel materials. Despite the advantages of combining different properties, synthesis constraints still remain. The major limitations of sol–gel processing for coating metals are delamination, crackability, adhesion, and thickness limits. Assuring a uniform distribution on the substrate and thermal treatments (curing/drying) are crucial factors to ensure the quality of anticorrosive coatings. 3 Cracks may affect several properties and are detri- mental to the substrate in wet corrosive media. Sendova et al. 255 produced silicate sol–gel coating films with four different crack patterns, achieving reproducible patterns by controlling the film deposition parameters. These authors showed that the geometric characteristics of the crack patterns were related to the Table 7: Studies on corrosion protection using OIH (class II) sol–gel coatings on magnesium substrates published since 2001 Year Precursors Results and conclusions References 2005 MAPTS, MPTMS, SiO 2 OIH coatings provided corrosion protection by sealing pores in the anodized layer and acting as a barrier. The application of multilayers eliminated the diffusion paths for corrosive species 234 2006 TEOS, PHS Besides the barrier coating on a metal surface, the phosphonate functionalities reacted with the surface of the substrate increasing both adhesive and corrosion resistance properties of the coatings 235 2008 GPTMS, ZrTPO, TBADP A well-adhered OIH gel coating for the substrate was obtained and the effectiveness of corrosion protection was confirmed 236 2009 TEOS, MTES, DEDMS, PHS, GPTMS Corrosion protection was improved by implementing an interpenetrating network coating morphology 237 TEOS, GPTMS Study of the OIH coating properties, characterization and formation mechanism 238 GPTMS, TMOS Phosphate conversion coating sealed with OIH coating doped with inhibitor (2-methylpiperidine) showed better corrosion resistance than undoped coating 239 TEOS, GPTMS Three layers of OIH coatings totally covered the cracks produced on the molybdate conversion coating first deposited on the substrate and showing good corrosion behavior 240 2010 ZrTPO, GPTMS OIH gel coatings doped with corrosion inhibitor showed improved corrosion behavior in the protection of the films in comparison with the undoped ones 241 TMOS, DEDMS OIH coatings obtained were evaluated as autonomous protective coatings as well as a pretreatment prior to acrylic topcoat. OIH coatings doped with Ce 3+ were effective as pretreatments for a final acrylic coating 242 GPTMS, VTES Increasing of [Ce 3+ ] on the OIH coating decreases the anticorrosion effect 243 2011 TEOS and MTES Precursor ratios (X1), sol dilution (X2), and sintering temperature (X3) were studied for an OIH coating. Best conditions obtained for X1 = 3.36,
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  • Fall '19
  • 1984, oIh, OIH coatings

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