Trivalent chromium conversion coatings have been deposited onto aluminum 2024-T3 alloy by immersion into or by spraying on a solution of chromic sulfate and hexafluorozirconate for periods of time varying from 3 minutes to 5 days. This treatment was followed by the deposition of hybrid silicate materials containing different organic modifiers [vinyl, methacrylate, epoxide functionalities and poly(2-ethyl-2-oxazoline)] to produce composite coatings. Aluminum alloys coated with the
composite films, as well as single-layer coated aluminum alloys, i.e. coated with the conversion coating or the silicate film, were tested by a 168-hour salt spray technique. Significantly better corrosion resistance was observed for composite films, which exhibit significantly less localized pits and corrosion areas, as compared to the single-layer coated aluminum alloys. The effect oftrivalent chromium treatment and its duration, as well as the silicate composition and synthesis conditions on
corrosion resistance of the resultant coatings are discussed. Keywords: trivalent chromium conversion coating, AI 2024-T3 alloy, sol-gel, hybrid organic modified silicate (ORMOSIL) coating, silanes, corrosion resistance, salt spray testing.