Dealloying Dealloying is a rare form of corrosion found in copper alloys, gray cast iron, and some other alloys. It can also occur by redeposition of the noble component of the alloy on the metal surface.
Control is by the use of more resistant alloys inhibited brasses and malleable or nodular cast iron.
The brass on the left dezincified leaving a porous copper plug on the surface. The gray cast iron water pipe shown on the right photo has graphitized and left graphitic surface plugs which can be seen on the cut surface. The rust tubercules or bubbles are also an indication of pitting corrosion . Stagnant seawater is so corrosive that even this normally corrosion-resistant alloy has corroded. Virtually all copper alloys are subject to dealloying in some environments.