Preparation and oxidation resistance analysis of ceramic coatings for prebaked anodes

An oxidation resistance coating is proposed to reduce the oxidation of electrolytic aluminum prebaked anodes. Sodium silicate (Na₂O·3SiO₂) and potassium silicate (K₂O·3.3SiO₂) serve as the binders, while alumina and silica serve as the ceramic fillers. The curing conditions of the coatings and the slurry composition are experimentally investigated to evaluate their effects on coating structure and performance. The results show that when the final curing temperature is 150 °C, the conversion rate of -Si-OH groups reaches 98.92 %. The -Si-O-Si- networks in the coatings are pivotal to avoid defects such as cracks, pores in the coating. And the addition of fine SiO₂ particles improves the three-dimensional network structure of the coating and hinders the expansion of cracks. When the binder-to-filler mass ratio (BFMR) is 0.9 and the SiO₂ content in the filler is 30 %, the coating is uniform and dense with least cracks, pores, bulges or bubbles. After oxidation at 900 °C for 72 h, the mass loss of the optimized coated samples is only 0.60 %.