Fe - 25 % Cr 강재에 소량의 Al 첨가가 고온 부식에 미치는 영향

The corrosion of Fe-25w/o Cr steel, containing of 0-4.2 w/o Al, has been investigated over the temperature range of 700℃ to 1000℃ in the salt of 90 w/o Na₂SO₄-10 w/o NaCI. The result is as follows: 1) At 700-800℃, the corrosion is hardly proceeded after 24 hrs. But, above 900℃, an addition of 2.3-4.2 w/o Al is desired for protecting the corrosion attack. 2) The corrosion attack is proceeded through the grain boundary. 3) When the specimen of O w/o Al is corroded for 36 hrs, CrS is detected above 800℃. But, in case of 1.1-4.2 w/o Al, CrS is detected above 900℃. 4) By SEM, a larger addition of Al leads α-Al₂O₃scale to be protective, and it decreases the velocity of corrosion. 5) By EPMA, the scale is produced in order of iron-oxide, chrome-oxide, and aluminum-oxide. It arises because each atoms migrates to the surface of specimen on the high temperature.