Characterization of Cerium-based Conversion Coatings for Corrosion Protection of Aluminum Alloys
Cerium-based conversion coatings were formed by a spontaneous reaction between a water-based solution containing CeCl3 and aluminum alloy 7075-T6 substrates. Coating performance was evaluated in neutral salt fog according to ASTM B117. Coating microstructure and thickness were observed by scanning electron microscopy (SEM). Coating composition and the cerium oxidation state were characterized using energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) respectively. The morphology and salt fog performance of cerium conversion coatings were affected by pre-treatment of the panel prior to coating. The best pre-treatment consisted of desmutting, degreasing, and acid activation. After immersion in the coating solution for 30 s, Ce-rich deposits formed on the 7075 surface. After 5 min, coatings consisted of Ce-rich particles in a Ce-containing matrix. Immersion times of 5 min or longer produced coatings that could pass published military requirements for conversion coating performance in neutral salt fog. XPS analysis showed that the coatings contained Ce4+.
M. OKeefe et al., "Characterization of Cerium-based Conversion Coatings for Corrosion Protection of Aluminum Alloys," Surface and Coatings Technology, Elsevier, Jun 2002.
The definitive version is available at http://dx.doi.org/10.1016/S0257-8972(02)00062-2
Materials Science and Engineering
Keywords and Phrases
Aluminum Alloy 7075-T6; Cerium; Conversion Coating; Corrosion Protection
Article - Journal
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