Selective leaching/dealloying

When one element of a solid alloy is removed by corrosion, the process is known as selective leaching, dealloying, or dezincification. The most common example is the removal of zinc from brass alloys that contain more than 15% zinc. When the zinc corrodes preferentially, a porous residue of copper and corrosion products remains. The corroded part often retains its original shape and may appear undamaged except for surface tarrush. However, its tensile strength, and particularly its ductility, are seriously reduced. 

Selective corrosion, also called selective leaching or dealloying, implies the selective dissolution of one of the components of an alloy that forms a solid solution. It leads to the formation of a porous layer made of the more noble metal. 

Selective leaching or dealloying is the selective removal of one element from an alloy by corrosion processes. The most common example is the selective removal (dezincification) of zinc in brass alloys. Dezincification may either be plug-type or uniform. In other alloy systems, aluminum, iron, cobalt, nickel, chromium, and other elements may be selectively removed [49]. Little work has been done in differentiating susceptibility of selective leaching of alloys in synthetic and naturtil seawater [6]. 

Corrosion in which cobalt is selectively leached from cobalt-based alloys, such as SteUite, or from cemented carbides. See also dealloying and selective leaching. 

As noted previously, dealloying also affects pre-boiler components manufactured of cast iron, such as FW pumps and valves. These components may, under certain (long-term) circumstances, suffer a selective form of preferential leaching galvanic corrosion. Specifically, graphitic corrosion may take place when the (anodic) iron matrix con-... 

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