Abstract: In a process for the mechanical cleaning of heat exchange surfaces of an evaporator or superheater of a steam generator, a dust-laden hot waste gas being passed through the steam generator, the formation of adhesive deposits on the heat exchange surface is prevented by lowering surface temperature at least at the beginning of a cleaning cycle. The surface temperature will be reduced to below the softening temperature of the material being deposited whereby such material forms hard deposits which may be loosened from the surfaces by mechanical means such as vibration.