Organic–inorganic hybrid sol–gel coatings for corrosion protection of aluminum alloys

Chromium-based pretreatments are among the most successful systems for aluminum-based alloys, however, due to environmental and health concerns, chromium-based compounds are a target for replacement. Sol–gel approach has emerged as a versatile method for preparing a host of sol–gel hybrid coatings that are candidates for use in protective coating applications. Organic–inorganic hybrid sol–gel coatings are among the most attractive alternatives to the use of chromium-based coatings because they are highly adherent and chemically inert coatings that are covalently bonded on the metal substrates at low temperature near ambient. In this review, the authors aim to summarize the latest achievements and strategies for the sol–gel process parameters as well as other factors that influence the corrosion properties of the organic–inorganic hybrid sol–gel coatings for the corrosion protection of aluminum-based alloys. The authors also discuss the existing issues and challenges in anticorrosion performance of the organic–inorganic hybrid sol–gel coatings.