Emission of pollutants from automobiles is regarded as one of the major causes of air pollution in many cities around the world. However, the pollutants could be almost eliminated by using catalytic purification of exhaust gas, thus making a better environment. The metallic material for catalytic converters made of ferritic stainless steel, Sandvik 0C404 (20.0 Cr-5.0 Al-Fe balance in wt % plus the addition of rare earth elements), offers a number of advantages over a ceramic one: better thermal conductivity, higher mechanical strength and toughness, thinner walls, larger effective area, greater catalytic capacity, smaller and more flexible design; better resistance to thermal shock. The formation of a homogenous A12O3 layer at high temperature is essential for providing corrosion resistance in such applications because of its high corrosive environment.

A prolonged oxidation of ferritic stainless steel Sandvik 0C404 at 1100 °C resulted in an accelerated oxidation (as schematically illustrated in Fig.l).