AbstractThe effects of a range of acidic and alkaline reagents on the electrodischarge machined (EDM) surface of AISI D6 tool steel have been investigated. The acidic reagents were found to attack mainly the underlying parent metal at the roots of fine fissures in the recast layer, causing severe localised pitting of the EDM surface. The alkaline reagents, however, reacted strongly with the recast layer, giving rise to an evenly pitted surface. The results indicate that the majority of the globule appendages produced by EDM are fused firmly on to the recast layer. They become an integral part of the surface and cannot be easily dislodged by chemical means.