Sealing of pores in sol–gel-derived tritium permeation barrier coating by electrochemical technique

Abstract

An electrolytic deposition technique was applied to seal open pores in sol–gel derived ZrO2 coating and to improve barrier effects against permeation of hydrogen isotopes. Disk-type specimens of type 430 ferritic stainless steel were first covered by thin ZrO2 films (50nm) with a conventional sol–gel technique. Then, pores in the ZrO2 film was sealed with ZrO2 or Al2O3 by cathodic processes in ethanol solution of Zr or Al nitrate and subsequent heat treatments in air. The permeation rate of hydrogen was measured at 300–600°C. The sol–gel derived ZrO2 coatings showed only limited barrier effects; the permeation reduction factor (PRF) was about 6–800. Nevertheless, the treatments by electrolytic deposition technique resulted in considerable improvement in the barrier effects, especially at high temperature region (>500°C), and the PRF increased to 100–1000.