Response of nanocrystalline cerium-based conversion coatings on Al 2024-T3 to chloride environments

Nanocrystalline cerium-based conversion coatings were found to be effective at retarding corrosion of Al 2024-T3 in sodium chloride environments. Cerium oxide coatings were deposited by spraying an aqueous solution made with cerium chloride onto cleaned panels. After deposition, the coatings were treated in a phosphate solution, which produced dense, nanocrystalline coatings composed of hydrated cerium phosphate. Visually, the coatings appeared to inhibit corrosion and the formation of salt tails for at least 14 days in ASTM B117 neutral salt spray corrosion testing. Cross-sectional imaging using transmission electron microscopy and compositional depth profiling using Auger spectroscopic analysis after salt spray exposure revealed that an aluminum oxide layer was present on the surface of the cerium phosphate coating.