Organic-inorganic hybrid sol-gel coatings for metal corrosion protection: a review of recent progress

This paper is a review of the most recent and relevant achievements (from 2001 to 2013) on the development of organic-inorganic hybrid (OIH) coatings produced by sol-gel-derivedmethods to improve resistance to oxidation/corrosion of different metallic substrates and their alloys. This review is focused on the research of OIH coatings based on siloxanes using the sol-gel process conducted at an academic level and aims to summarize the materials developed and identify perspectives for further research. The fundamentals of sol-gel are described, including OIH classification, the interaction with the substrate, their advantages, and limitations. The main precursors used in the synthesis of OIH sol-gel coatings for corrosion protection are also discussed, according to the metallic substrate used. Finally, a multilayer system to improve the resistance to corrosion is proposed, based on OIH coatings produced by the sol-gel process, and the future research challenges are debated.