Materials used in space vehicles are subject to aggressive thermal environments. These materials are mainly employed in rocket engine exhaust nozzles and surfaces exposed to the severe atmosphere during atmospheric reentry. Laboratory testing is crucial for qualifying the materials used in thermal protection systems of space vehicles. In this study, it is proposed to simulate the process of thermal oxidation in ceramic compounds inside the plasma tunnel - ITA, to achieve this objective a hypersonic plasma system was used that has a pre-nozzle that controls the insertion of gas in the system. The inclusion of a pre-nozzle allows us to enhance the characteristics of the vacuum system to meet the specific requirements of our experiments. The plasma setup generates a hypersonic thermal flow, which enables us to investigate the thermal oxidation of ultra-high temperature ceramic composites, particularly Zirconium Diboride (ZrB2). To explore the oxidation mechanisms and microstructural properties under hypersonic thermal flow, we prepared ZrB2 samples with varying volumes of Silicon Carbide (SiC): 10%, 20%, and 30%. The oxidation tests yielded insightful results. Samples containing 10% and 30% SiC experienced active oxidation, resulting in the formation of an unstable and fragile Zirconium Oxide (ZrO2). Unfortunately, this ZrO2 layer proved insufficient in withstanding the drag force and thermal flux of the hypersonic plasma jet, leading to partial volatilization of the oxide layer and significant mass loss. However, for the oxidation tests involving the sample with 20% SiC, we observed a mass gain due to the formation of a Zirconium Silicate (ZrSiO4) passivation layer. This passivation layer, a stable oxide, which, not only promotes mechanical resistance but also exhibits a low degradation rate. These findings can be attributed to the variation in SiC content, with an ideal proportion of 20% SiC in ZrB2. This proportion significantly influences the oxidation mechanisms, resulting in the formation of a protective layer.