Closure

Fuel contaminant corrosion of fiber-reinforced composites, specially processed metals and others defined as "advanced materials" in the Introduction has not been discussed, mainly because the open literature contains little on the topic. On the other hand, one would hope that corrosion of such materials could often be treated not as "new", but simply as combinations of known corrosion systems on which knowledge, as described above, is available.

As for new directions in corrosion research, one need (obviously dear to the author) would be to quantify how much ceramic corrosion is influenced by oxide acid-base reaction—championed strongly here--and how much by other types of bondings, diffusion processes, ionic radii, or other factors. For example, solubilities of the type provided by Rapp (Fig. 1) for oxides in molten Na2S04, but for the high temperature Na20-V205 and

Na20-P205. systems, could, prove informative. It may be found that as .the acidic , ;.. components become more capable of network formationti(i.e.,,;with P2Os), the acid-base reactivity; trends, may change; so. that oxides resistant , ¡to, one, acidic, salt-system (Zr02 to Na2S04/S03; or NaV03) may not be , resistant, ,to; a .secpnd, system (Zr02 to, Na20-P2O5}.;' ' '' 'U -

Finally, physical^.processing: should not be-;neglected as-a means for improving corrosion performance of ceramics or other advanced materials;|Pr,ocessing0that > improves; ,c,hemical^homqgen^ easy diffusion path's, reduces, reactive ; impnritv r.nntent _nr devel00s.•b.epefi.ciaJ. phase, structure .may substantially increase corrosion: resistance .even of materials,, containing , known (e.g:. Y203) reactive components. .:

Research, ¡bj^the author was sponsored under the NAySE^v. ;Pr,ogramr for Ship: Propulsion Technology,uandvthe. support is gratefully acknowledged..; ,, ;...;:

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