SiC-based components are sometimes susceptible to aqueous dissolution in LWR coolant environments. To address this issue, similar to 10 mu m thick Cr coatings was deposited on reaction-bonded silicon carbide (RBSC) plates by magnetron sputtering. Corrosion behavior of Cr-coated SiC and -uncoated SiC coupons was studied by immersing in autoclave (345 degrees C and 16.5 MPa). The weight loss of the Cr coated SiC coupons (3.02% after the 93-days) in the autoclave tests was effectively reduced due to their Cr-coated surfaces, in contrast to the uncoated ones (20.4% after the 78-days). Moreover, microstructural and compositional evolutions were examined by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. It was revealed that a continuous and dense Cr2O3 layer formed on the surface after the hydrothermal corrosion, which can suppress the in-diffusion of corrosive medium.