Corrosion Behavior of Silicon Carbide in 290°C Water

The fundamental corrosion behavior of silicon carbide (SiC) ceramics was investigated after immersion in 290°C water solutions with different pH and dissolved‐oxygen concentrations. The weight loss in the oxygenated solution was more than that in the deoxygenated solution and was accelerated by increasing pH. Preferential attack could be found at grain boundaries and around pores on the sample surface immersed in the oxygenated alkaline solution. The weight change, dW, followed the general rate law, (dW) m = kt. The exponent, m, was 1.11 in the alkaline solution and 0.45 in the acidic solution. Based on the above results, the SiC was considered to be directly hydrolyzed to a silica sol, with its dissolution kinetics dependent on the sol stability. This corrosion behavior is quite different from those in high‐temperature or vapor‐phase hydrothermal oxidation, where the oxidation rate is controlled by oxidant diffusion through the protective silica surface layer.