Cerium-rich conversion coatings have been deposited onto aluminium 2024T351 alloy by immersion into a solution containing 10 g L-' CeCl, and 1% H,O, in a process described as 'cerating'. Prior to deposition the alloy had been prepared either by using a standard chemical pretreatment used for aerospace alloys before conversion coating or by polishing. X-ray photoelectron spectroscopy and scanning electron microscopy have been used to characterize these ceriumcontaining conversion coatings. It was found that, during deposition, hydrated cerium oxide initially covered the intermetallics present in the alloy surface and then covered the surface generally. Deposition continued over the intermetallics throughout the conversion coating process, resulting in thick, heavily-cracked regions considerably greater than the average thickness of the film (> 0.3 pm). Elsewhere the coating was generally up to 0.2 pm thick, and appeared to comprised of deposited particles around 100 nm in size.
The effect of a pretreatment sequence on several aluminium alloys was examined by X-ray photoelectron spectroscopy and SEM. The pretreatment consisted of vapour degreasing followed by a three step sequence comprising 1 min immersions in (a) nitric acid -hydrofluoric acid solution, (b) sodium hydroxide solution and (c) a 1 or 5 min immersion in nitric acid -hydrofluoric acid as in step (a). Following each pretreatment step the alloy panels were rinsed in tap water for 1 min. The surfaces of aluminium alloys 2024-T3, 6061-T6, and 7075-T6 were examined at each stage in the pretreatment process. The neutral salt spray resistance of specimens deoxidised with this pretreatment and chromate conversion coated were compared to those deoxidised with a conventional chromate based deoxidiser before conversion coating.MST/4920
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.