沸騰硝酸中のステンレス鋼製管材へのカソード防食効果の検討

An Application of cathodic protection of stainless steel tube in boiling nitric acid

上野 文義  ; 山本 正弘 ; 加藤 千明   ; 垂井 宏文; 蝦名 哲成*; 下川原 茂*; 加納 洋一*

Ueno, Fumiyoshi; Yamamoto, Masahiro; Kato, Chiaki; Tarui, Hirofumi; Ebina, Tetsunari*; Shimogawara, Shigeru*; Kano, Yoichi*

ステンレス鋼製再処理用機器への外部電源方式によるカソード防食法の適用可能性を示すことを目的に、SUS304ULC製管材の外面を対象としたカソード防食試験を行った。その結果、平均24mの減肉量が、カソード防食により陽極との位置に関係なく3mまで均一に低減できた。これらの結果と、過不働態域の腐食はおもに電位の影響を受けること、沸騰硝酸の電気伝導率が高く均一な防食効果が期待できることと、腐食がおもに電位による影響を受けると考えられることから、カソード防食法がステンレス鋼製再処理用機器の耐食性改善のために適用可能と考えられる。

An application of cathodic protection method with impressed current system to control corrosion of austenitic stainless steel in boiling nitric acid solution was studied to improve corrosion resistance of components in fuel reprocessing plant. Tube type specimens made of ultra low carbon type 304 stainless steel (SUS304ULC) were immersed in boiling nitric acid solutions using electrochemical test cells, electrochemical potentiostatic tests and cathodic protection tests were performed. Corrosion rates in the solution with and without protection were measured. As the results, loss of outer surface thickness of the tubes was decreased about 1/8, and no deviation of the loss was observed. Authors were concluded that cathodic protection method was expectative as one of the maintenance methods of components in fuel reprocessing plant.