Electrochemical roles of precipitates on uniform corrosion and hydrogen pickup of zirconium alloys, (II) - Roles on hydrogen pickup

Substantial roles of precipitates such as Zr-Fe-Cr type intermetallic compo unds on uniform corrosion and hydrogen pickup of zirconium alloys in pure w ater autoclave tests were investigated from an electrochemical point of vie w. In the previous paper, corrosion mechanism was elucidated by the anodic protection-precipitates degradation model. This paper describes the roles o n hydrogen pickup. 633 K pure water autoclave test was performed on high purity zirconium, Zr- 0.2Fe, Zr-0.2Cr, and Zr-9.1Fe-0.1 Cr alloys. Hydrogen analysis after the co rrosion test showed that hydrogen pickup ratio of Zr-0.2Fe alloy was about 80%. It was much higher than about 30% of pure Zr and about 10% of both Zr- 0.2Cr and Zr-0.1Fe-0.1Cr alloys. Larger hydrogen content was introduced int o Zr-0.2Fe alloy than the other ones by the cathodic hydrogen charging unde r coulomic equivalence. The precipitates at metal-oxide interface could act not only as cathodic sites in the anodic protection mechanism but also 'wi ndows' for hydrogen ingress.