腐食剤の酸化還元電位ならびに腐食剤中における各種ステンレス鋼および合金の腐食電位の測定

抄録

The redox potential of some etching reagents and the corrosion potential of various stainless steels and alloys were measured and the etching behavior of γ, α and σ phase in stainless steel were explained electrochemically. The results obtained were as follows: (a) In acid reagents, low-chromium ferritic and austenitic stainless steels are corroded but high chromium alloys fell into the passive state. For this reason when stainless steel containing σ phase is etched in acid reagents, γ or α phase are corroded and σ phase, higher in chromium than α or γ phase, is not corroded. (b) On the other hand, in alkaline reagents, low-chromium austenitic stainless steels are not corroded but high-chromium stainless steels and alloys are corroded and stained. For this reason, when stainless steel containing σ phase is etched in the alkaline reagents, γ phase is not corroded and α or σ phase are corroded and stained.