The solar furnace is a heating system based on concentrated sunrays on the material surface. It is an original method for testing ultra-high-temperature ceramics (UHTC) at very high temperature (above 2200°C) in air with an exposure time of several minutes. In this study, the solar flux is 15.5 MW.m-2 with a homogeneous exposed surface of 10 mm2. A large temperature-time composition parameters space is covered producing a large set of oxidized samples. Massive cylindrical specimens of UHTC materials are prepared by spark plasma sintering at 1900°C under a pressure of 100 MPa for 5 minutes. Then, samples are tested in air from 1750°C up to 2400°C with dwell times varied from 1 to 5 min. During oxidation of ZrB2-SiC (20%vol) material, the formed and known complex oxide scale identified from literature is easily reproduced using this method. It consists of a thin outer silica layer and zirconia columnar layer with a region of SiC depleted zone in ZrB2 phase. The impact of the reduction of Si content is quantified and the coating ZrB2-20%vol SiC is tested as protection on C-C composite.