A heat exchanger for cooling a hot gas that contains solid particles, comprising heat exchanger tubes through which the hot gas flows, with the tubes being surrounded by a casing, and with ends of the tubes being welded, via weld seams, into bores of respective tube plates disposed at the ends of the casing. A protective layer coats the end face of the gas inlet side tube plate, an inner wall of the bores, the weld seams, and an inlet region of the heat exchanger tubes. The protective layer comprises a metallic adhesive layer, a high temperature and erosion resistant ceramic layer, and a high temperature and erosion resistant metal layer disposed between the adhesive layer and the ceramic layer.