沸騰硝酸中へのCr,Vイオン添加によるステンレス鋼の腐食の時間変化

Change in corrosion of stainless steel in boiling nitric acid solution with Cr or V ions

本岡 隆文; 山本 正弘 ; 上野 文義  ; 加藤 千明   ; 石島 暖大 

Motooka, Takafumi; Yamamoto, Masahiro; Ueno, Fumiyoshi; Kato, Chiaki; Ishijima, Yasuhiro

高酸化性イオンが存在する硝酸溶液において、ステンレス鋼が加速腐食されることは既に明らかにされているが、高酸化性イオンの腐食力の時間変化挙動は明らかでない。そこで、Cr(VI)とV(V)の腐食力の時間変化挙動を、SUS304L鋼を用いた沸騰硝酸溶液中での腐食試験による腐食速度の測定及び溶液分析によるイオンの定量により調査した。Cr(VI)含有高濃度硝酸溶液中ではステンレス鋼の腐食速度は試験時間とともに急減しCr(VI)はCr(III)に還元していった。V(V)含有硝酸溶液ではテンレス鋼の腐食速度は試験時間によらずほぼ一定でありV(V)量に変化はなかった。Cr(VI)の腐食力によるステンレス鋼の腐食加速効果は硝酸濃度と時間に強く影響を受けるが、V(V)の腐食力によるステンレス鋼の腐食加速効果には時間依存性がないことが明らかとなった。

It is well known that stainless steels rapidly corrode in nitric acid solutions included oxidizing ions. But the time effect of oxidizing ions on corrosion has been rarely studied. In this repot, the change in corrosion rate with time was investigated using Cr(VI) and V(V) species. Corrosion test of SUS304L stainless steel was conducted in boiling nitric acid solutions. Quantitative analysis of test solutions was done before and after corrosion tests. Corrosion rate of stainless steel in high concentration nitric acid solution with Cr(VI) was rapidly decreased and Cr(VI) was reduced to Cr(III). Corrosion rate of stainless steel in nitric acid solution with V(V) and the amount of V(V) were not greatly changed with time. It was concluded that the corrosion of a stainless steel in nitric acid solutions included Cr(VI) was greatly affected by concentration of nitric acid and test time, and the corrosion of a stainless steel in nitric acid solutions included V(V) was not affected by test time.