corrosion that proceeds along planes parallel to the surface, generally at grain boundaries, forming corrosion products that create a wedging stress, giving rise to a layered appearance
NOTE This form of corrosion is associated with a marked directionality of the grain structure. Applied stresses are not necessary for exfoliation to occur. However, in alloys susceptible to stress corrosion cracking, the corrosion product wedging action undoubtedly contributes to the propagation of the exfoliation attack. It is important to note that some alloys not susceptible to stress corrosion cracking can suffer exfoliation corrosion. However, if the grain structure is equiaxed, exfoliation corrosion does not usually occur.