Investigation of the effect of surface transition on the formation of byproduct and flow marks during the electrochemical machining of 6061 aluminum

This study investigated the formation of protrusion-type flow marks during electrochemical machining of 6061 aluminum. The results indicate that the growth of a viscous, byproduct layer on the anode surface can occur rapidly within regions of the interelectrode gap where electrolyte flow velocity is very low. The growth in thickness of this viscous layer can slow down aluminum cation diffusion and thus the local material removal rate. Differences in the material removal rate between these regions and surrounding regions of smaller byproduct thickness led to protrusion-type flow marks. Once electrolysis ceases, the by-product is quickly stripped away from the anode surface by flowing electrolyte, even in regions of low flow velocity. Consequently, this byproduct is typically not observed after the anode is removed cathode-anode assembly. This study also indicates that an easy way to avoid this type of flow mark formation is to avoid large, step transitions in the anode surface. These should be replaced with gentler transitions that minimize electrolyte flow separation.