Time dependence on corrosion behavior of Ta in NaOH solutions

Ishijima, Yasuhiro ; Ueno, Fumiyoshi  ; Abe, Hitoshi 

In spent nuclear fuel reprocessing plant, Zr/Ta dissimilar metal joint is used for connect between different devices. And it is known that Ta corrodes in NaOH solutions. The other hand, it is not clear that the time dependency on corrosion behavior of Ta in NaOH solutions. This study aims to elucidate the effect on time dependency for corrosion behavior of Ta in NaOH solutions. Immersion tests and electrochemical measurements were carried out in NaOH solutions. Immersion test results show that corrosion rate in 6mol/L NaOH was decreased with time. And electrochemical measurement results suggested that the decrease of corrosion rate was caused by corrosion product film generation on the surface of Ta. The corrosion product was determined as NaTaO 24.5HO by Raman spectroscopy. From these results, it is considered that the decrease of corrosion rate was caused by the NaTaO 24.5HO film suppress the Ta dissolution.