Corrosion Behaviors of Al-Steel-Sputtering-Treated Steel and SiC/SiC Composites in High Temperature LBE at Low Oxygen Concentration

Corrosion tests of Al and SS-304-sputtering-surface treated STBA26 (9Cr.1Mo.0.1Si) and SiC/SiC composites with BN (boron nitide) coating has been conducted in high temperature LBE of 700°C at low oxygen concentration of 6.8 × 10⁻⁷ wt% and the behavior was analyzed. The sputtering technique was used to protect the steel from corrosion. The thickness of sputtering-treated layer was 21.45 μm. All specimens were immersed in LBE in a pot for 1000 hours. The STBA26 (9Cr.1Mo.0.1Si) without surface treated were also tested for comparison with sputtering-treated steels. The results showed that sputtering-treated layer still remained on the base of STBA26. No penetration of LBE was observed in this layer. The layer could protect the steel from penetration of LBE. The result also showed that thin layer which contains aluminum oxide and chromium oxide was formed on the surface-treated layer, and it protected the base area. On the contrary, the penetration in base area was observed in the as received STBA26. In SiC/SiC composites, there appeared cracks in a thin surface area and LBE penetrated deeply into the material. The corrosion did not occur in this SiC/SiC composite in the high temperature LBE.