| 摘要 |
PROBLEM TO BE SOLVED: To reduce the possibility of locally forming an abnormal passive film, furthermore to simplify the treatment and to reduce the cost. SOLUTION: Af first, stop valves 25 and 27 are closed, a stop valve 26 is opened, high purity impurity gas heated by a gas heating device 30 is circulated through the inner passage of the object 100 to be surface-treated. After that, the stop valves 25 and 26 are closed and the stop valve 27 is opened, then the high purity oxidizing gas heated by the gas heating device 30 is circulated through the inner passage of the object 100 to be surface-treated. In this way, on the metallic surface at the inner passage in the cleaned object 100 to be surface-treated, an oxidized passive film is formed.
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