ISSN:
1573-4889
Keywords:
corrosion mechanism
;
carbon dioxide
;
oxygen-18
;
iron-9% Cr alloys
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Oxide layers have been grown on Fe-9% Cr, Fe-9% Cr-0.3% Si, and Fe 9% Cr-0.6% Si alloys in carbon dioxide at 853 °K. It is known that such oxides are duplex, the outer layer being magnetite, formed by iron transport. The inner layer is Fe-Cr spinel but little is known about its growth mechanism so this has been investigated using oxygen-18 as a tracer. Oxides were grown first in C16O2 and then in C18O2 and the distribution of oxygen-18 in the scale measured using nuclear techniques. For all the alloys used, significant amounts of oxygen-18 were observed within the inner layer in addition to growth of18O-rich magnetite at the outer surface. The two possibilities of the oxygen-18 being present as a consequence of isotopic exchange or because new oxide had formed within the spinel layer are discussed. Our conclusion is that it is very unlikely that significant isotopic exchange had occurred in any part of the scale, and we deduce that at least a substantial amount of the oxygen-18 in the inner layer was deposited as a result of new oxide formation within that layer. The results also indicate that the location of growth sites within the inner layer differed between the alloys.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00603476
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