Antioxidant Coatings for Carbon Anodes in Aluminum Reduction Cells

Antioxidant coatings are an effective approach to reducing the additional consumption of carbon anodes during molten-salt aluminum electrolysis. In this article, low molar ratio cryolite was used as the coating material, while acrylic, vinyl acetate-ethylene (VAE), polyvinyl alcohol, and sodium carboxymethyl cellulose (CMC) were used as binders. Under laboratory conditions, high-temperature oxidation experiments conducted on coatings prepared with different binders show that the coating formulated with acrylic binder exhibits the best oxidation resistance. Porosity measurements of the sintered coatings indicate that the acrylic-based coating has the lowest porosity. Electrolysis experiments using these coatings further reveal that the acrylic-coated anode exhibits the lowest additional consumption. Scanning electron microscopy (SEM)–energy-dispersive X-ray spectroscopy (EDS) elemental mapping of the initial electrolyte revealed the presence of a small amount of silicon impurity. After electrolysis, X-ray diffraction (XRD) and XRF analyses of the electrolyte indicated that no additional impurity phases were detected. SEM–EDS mapping and X-ray diffraction (XRD) analysis of the cathodic aluminum further confirmed that a trace amount of silicon was present in the product, mainly in the form of aluminum silicate. High-temperature oxidation experiments and electrolysis tests consistently verified that the coating provided effective protection to the anode, while no deterioration in the purity of the primary aluminum was observed. Graphical