Abstract: An oxide film is formed on the surface of a sample made from a metal material by holding the above-described sample at a temperature of 800° C. or higher and 1,100° C. or lower in an oxygen-containing atmosphere, and the sample provided with the oxide film is immersed in a corrosive solution containing an acid and NaCl for a predetermined time. After immersion, the corrosion state (degree of denseness of oxide film, cracking state, and the like) of the sample is evaluated. The corrosion resistance of the sample can be evaluated appropriately and conveniently in a short period of time by causing accelerated corrosion in an environment simulating the actual environment of an internal combustion engine.

Abstract: An electrode material contains, on a mass percent basis, Al: 0.005% to 0.2%, Si: 0.2% to 1.6%, Cr: 0.05% to 1.0%, Ti: 0.05% to 0.5%, and Y: 0.2% to 1.0%. The remainder are Ni and inevitable impurities. The Si/Cr mass ratio is 1 or more. Because of the inclusion of specific amounts of Al, Si, Cr, and Y and the Si content higher than the Al content, the electrode material has an oxidation inhibiting effect. The inclusion of the specific amount of Ti can reduce the occurrence of expansion and cracking of the oxide film. Because of the inclusion of the specific amount of Y, the oxide film can maintain the microstructure even at high temperatures and have high resistance to high-temperature oxidation. Having a Si/Cr ratio of 1 or more, the oxide film has improved corrosion resistance and is resistant to corrosion by corrosive liquids.