A comparative study on the anodic behavior of Cu65Ni20Fe15 and (Cu65Ni20Fe15)(98.6)O-1.4 materials during the electrolysis of aluminum was conducted. Both materials were prepared in powder form by ball milling and subsequently consolidated to form dense pellets that were used as anodes. The electrochemical characterization was performed at 700 degrees C in a potassium cryolite-based electrolyte, and the composition-morphology of the oxide scales formed on both anodes were determined by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction measurements. On Cu65Ni20Fe15, a thick (170 mu m) and porous oxide scale is formed after 15 min of electrolysis that readily dissolves (or spalls) before a denser oxide layer is formed after a longer electrolysis time (1 and 5 h). In comparison, a thin (2 mu m) and dense oxide layer mainly composed of NiFe2O4 is observed on a (Cu65Ni20Fe15)(98.6)O-1.4 electrode after 15 min of electrolysis. The thickness of this oxide layer increases to 10 and 30 mu m after 1 h and 5 h of electrolysis. However, the outward diffusion of Cu to form CuOx at the surface of the electrode is not totally hampered by the presence of NiFe2O4 and a porous Cu-depleted region is formed at the oxide/alloy interface. As a result, electrolyte penetration occurs in the scale, which favors the progressive formation of an iron fluoride layer at the oxide/alloy interface. (C) 2013 Elsevier Ltd. All rights reserved.