Effect of Coating Parameters on the Microstructure of Cerium Oxide Conversion Coatings
Lavernia, E. J.
The microstructure and morphology of cerium oxide conversion coatings prepared under different deposition conditions were characterized by transmission electron microscopy (TEM). The coatings were formed by a spontaneous reaction between a water-based solution containing CeCl3 and aluminum alloy 7075-T6 substrates. Microstructural characterization was performed to determine the crystallinity of the coatings and to obtain a better understanding of the deposition parameters on coating microstructure. The results of TEM imaging and electron diffraction analysis indicated that the as-deposited coating was composed of nanocrystalline particles of a previously unreported cerium compound. The particles of the coatings produced using glycerol as an additive were found to be much finer than those of the coatings prepared in the absence of glycerol. This indicates that glycerol may act as a grain refiner and/or growth inhibitor during coating deposition. After deposition, the coated panels were treated for 5 min in a phosphate sealing solution. The sealing treatment converted the as-deposited coating into hydrated cerium phosphate. Panels coated from solutions containing no glycerol followed by phosphate sealing performed poorly in salt fog tests. With glycerol addition, the corrosion resistance of the coatings that were phosphate sealed improved considerably, achieving an average passing rate of 85%.
B. Y. Johnson et al., "Effect of Coating Parameters on the Microstructure of Cerium Oxide Conversion Coatings," Materials Science and Engineering: A, Elsevier, Nov 2003.
The definitive version is available at http://dx.doi.org/10.1016/S0921-5093(03)00516-1
Materials Science and Engineering
Keywords and Phrases
Cerium Hydroxide; Glycerol; Conversion Coatings; Corrosion Protection; Phosphate Sealing
Article - Journal
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