HIGH TEMPERATURE CORROSION RESISTANCE OF METALLIC MATERIALS IN HARSH CONDITIONS

Highly efficient energy recovery from renewable sources and from waste incineration causes new problems of corrosion at high temperature. A similar situation exists for new recycling processes and new energy storage units. These corrosions are generally considered to be caused by ashes or molten salts, the composition of which differs considerably from one plant to another. Therefore, for the assessment of corrosion-resistance of advanced materials, it is essential to precisely evaluate the corrosion rate under conditions close to industrial conditions. To be able to advise their customers in selecting the right material or the right protective coating, the present authors are developing testing equipment and related procedures to assess the high temperature corrosion rate of metallic materials. This paper describes the testing equipment developed so far and presents the first results obtained in two corrosive environments: the aggressive condensates that affect waste incinerators (mixture of liquid/solid salts in oxidising conditions) and heat transfer fluids of electric power generating plants based on solar towers (mixture of liquid salts). Temperatures range from 400 to 650°C. Tested materials include 16Mo3 (0.3% molybdenum steel alloy), Inconel 625 (austenitic nickel-chromium-based superalloys), Nickel 200, Ni-57CrMoSiB (nickel-base coating with high chromium content and boron as additional element) and Grade 91 (9% chrome- 1% molybdenum steel alloy).