Long-Term Testing of WC–Ni–Fe Coating as an Inert Anode in a Low-Temperature Electrolyte for Aluminum Production

Abstract

The behaviour of WC-Ni-Fe coating on 2Cr13 and X3CrNiMo18-12-3 stainless steel substrates was investigated in the context of their application as inert anode materials in a low-temperature (850 °C) electrolyte (50 wt.% AlF3-45 wt.% KF-5 wt.% Al2O3) by long-term testing around 50 h for aluminum production. The results show that the materials were corroded in a controlled manner and the extrapolated corrosion rates of WC–Ni–Fe/X3CrNiMo18-12-3 anode was 5.8 cm per year, which is acceptable from an industrial perspective. The total contamination level of anode constituents in the deposited metal was as low as 0.283 wt.%. These encouraging results seemed to be related in part to the X3CrNiMo18-12-3 substrate that allows only very slow penetration of oxygen atoms into the inner part. Post-electrolysis examination of the anodes indicates that the substrate material is one of the most important factors that determine the erosion resistance of coating inert anode. The results of electrolysis using 2Cr13 and X3CrNiMo18-12-3 substrates indicate that the electrical current is another important factor for the erosion resistance of inert anode coatings.

Keywords

• carbide
• ceramics
• coatings
• corrosion
• oxidation
• electrical conductivity