A Comparison of Bulk Precipitated Cerium Oxide Powders and Cerium Conversion Coatings and the Influence of Hydrogen Peroxide on Their Formation (Preprint)
Abstract
To better understand the role of hydrogen peroxide in the formation of cerium conversion coatings and precipitates, hydrated cerium oxide/hydroxide materials obtained from aqueous solutions have been characterized by thermogravimetic methods, X-ray diffraction, and scanning electron microscopy. Powders were prepared by precipitation with sodium hydroxide from cerium (III) chloride solutions using either hydrogen peroxide or oxygen sparging to oxidize Ce(III) species to Ce(IV) species. Cerium conversion coatings were deposited on Al 7075-T6 substrates using a spontaneous immersion process in a water-based solution containing CeCl3 and hydrogen peroxide. The results suggest that the cerium powders produced in the presence of hydrogen peroxide bear the most resemblance to the cerium conversion coatings, and that simulating the cerium conversion coating process through bulk precipitation tests is reasonable. Other significant observations were also made. One was that hydrogen peroxide lowers the pH required to precipitate cerium. Another was that a significant amount of oxygen was evolved upon heating both the cerium conversion coating and the cerium precipitates formed by using hydrogen peroxide as an oxidant. Lastly, the effect of hydrogen peroxide in the cerium conversion coating process is considered from the standpoint of corrosive attack on the aluminum substrates.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2006
- Accession Number
- ADA458368
Entities
People
- J. O. Stoffer
- Paul K. L. Yu
- S. A. Hayes
- T. J. O'keefe