DEALLOYINGis a corrosion process in which
one or more elements are selectively dissolved,
leaving behind a porous residue of the remaining
element(s). For example, in the silver-gold system,
silver can be almost 100% removed in various
acid electrolytes, leaving behind porous
gold, as shown in Fig. 1. This bicontinuous
metal-void structure is highly brittle in nature
and has been linked to stress-corrosion cracking
in many alloy systems (Ref 1–6). The seasonal
cracking of brass is perhaps the best recognized
(Ref 7). Perhaps the first detailed investigation in
the scientific literature on alloy corrosion was
reported by Calvert and Johnson in 1866 (Ref 8)
on copper-zinc alloys. Beyond its direct relevance
to stress-corrosion cracking, interest in the dealloying
phenomenon extends to the accelerated
corrosion in aluminum alloy 2024-T3 (Unified
Numbering System, or UNS, A92024) (Ref 9, 10)
and the development of high-surface-area electrodes
(Ref 11) and catalysts