Oxidation and corrosion of highly alloyed Cu–Fe–Ni as inert anode material for aluminum electrowinning in as-cast and homogenized conditions

As-cast and homogenous alloys of Cu–Fe–Ni with mass fraction of copper ranging from 10 to 70 wt.% and mass ratio of Fe and Ni of about 1:1 are investigated for application as anode material for the electrolysis of aluminum. The two-phase as-cast microstructure acts as a galvanic couple and enhances the corrosion rate during oxidation and electrolysis. Thermogravimetry oxidation studies and laboratory electrolysis tests show that previously homogenized anodes performed significantly better than as-cast anodes. The phenomenon of homogenization and discontinuous coarsening is addressed, including a phase diagram calculation.

► Thermogravimetry oxidation studies and laboratory electrolysis tests of Cu–Fe–Ni alloys in highly alloyed concentrations. ► Interesting for application as inert anode material for the electrolysis of aluminum. ► This work shows that the two-phase as-cast microstructure acts as a galvanic couple and enhances the corrosion rate. ► Previously homogenized anodes or finely decomposed alloys performed significantly better than as-cast anodes. ► Phase diagram calculation.