Mechanical properties and adhesion of oxide films examined by a solid particle impact method at high temperature corrosive environments

The surface degradation of metals such as boiler tubes and turbines in high temperature corrosive environments has caused a severe problem in fuel combustion power plant systems. The damage to materials has been often accelerated by mechanical removal of corrosion product formed on the material surface. It is therefore very important to investigate mechanical properties and adhesion of the films in practical high temperature environments, in order to discuss the acceleration of oxidation and life time of materials. Corrosion/oxidation tests were conducted for mild steel in high temperature corrosive environments of wet air, water steam with hydrogen chloride to look into basic behaviour of degradation of the metal and the growth of oxide films as corrosion products. It was found that oxide films were mainly formed on the specimen surface and their growth was accelerated by the corrosiveness of the environment. Impact tests were performed on the surface of mild steel covered with oxide films in the same environments to obtain mechanical properties and adhesion of the oxide films. It was found that the corrosive environments increased oxidation of mild steel a little, and that decreased the fracture strength and other mechanical properties of the oxide films. A strongly corrosive environment increased adhesion of the oxide films.