During the atmospheric reentry of a spacecraft, the dissociated flow around its Thermal Protection System (TPS) could travel from a low catalytic to a high catalytic surface. In this situation a peak of heat flux is experienced at the junction between the two materials. A safe vehicle design cannot preclude investigations on such a phenomenon, since the consequent heating could be harmful for the integrity of TPS. The present work finds its framework on the EXPERT (European eXPErimental Re-entry Testbed) project. The EXPERT vehicle TPS is composed of a C/SiC nose and a PM1000 skirt, so that a catalytic transition occurs in correspondence of their junction. Experiments on wall catalysis phenomena over Thermal Protection Materials (TPM) are performed in this project, using the von Karman Institute (VKI) induction-coupled plasma generator (Plasmatron), under operating conditions representative for real flight situation. Infrared thermography and pyrometry temperature measurements are performed in order to experimentally prove and quantify the transition.