(488aj) Microstructure Changes of RBSC in Boiling Sulfuric Acid Solutions

IS (Iodine sulfur) process is one of the candidate processes for use of in a very high temperature gas cooled reactor (VHTR) due to its high temperature energy in the nuclear power industries. The IS process is efficient and promising for a hydrogen production, however, the highly corrosive environment of this overall process limits an application of this process for a H2 production. Therefore, the corrosion behavior of special materials was an important parameter for a material's integrity assessment

The corrosion behavior and microstructure changes of reaction-bonded SiC in boiling 98wt% H2SO4 solutions is studied using the mass-loss technique. A weight gain whose amount was increased with the immersion time up to 100 days was observed. Nevertheless, the corrosion rate diminishes initially with time and tends to stabilize for long exposure times. After 120 days exposure time, the weight gain was saturated and decrease with time, while the rate is constant during this exposure time. It means that an oxide film is formed on the surface of a specimen during an immersion and the formed oxide thickness increases with the immersion time up to 100 days. After 120 days, there is no weight gain occurred on the sample, it means that dense oxide layer (about 25um thickness) was formed on the surface. The surface morphologies were examined by using SEM-EDS. A passive silicon oxide layer on a Si/SiC surface is attributable to the corrosion resistance for RBSC in boiling 98wt% sulfuric acid.