The active cooling of the Supersonic Combustion Ramjet engine, for hypersonic flight purpose, is ensured thanks to fuel, n-dodecane for the present study. The endothermic fuel pyrolysis, starting above 800 K, could generate an unwanted coke formation. Experimental tests up to 1125 K and between 1 MPa and 6 MPa have been performed on the hydrocarbon fuel pyrolysis to evaluate the coking activity. 316L stainless steel, low carbon steel and titanium reactors have been considered. A witness of the coke formation, based on its thermal insulation and pressure loss effects, has been found. A correlation between methane production and coke deposit was found. The coke has been studied with Scanning Electron Microscope (SEM), Energy Dispersion Spectroscopy (EDS), X-ray diffractometer and Fourier Transform Infrared (FTIR) spectroscopy. The porosity, the density and the permeability of the coke have been estimated. (C) 2008 Elsevier B.V. All rights reserved.