Effects of hydrogen on corrosion of pure Ni in high temperature water

Highlights: •Cyclic change of CER and E_corr is observed during cyclic change in environment. •Ni oxidation was enhanced by the hydrogen in metal. •Ni oxide can be reduced by the hydrogen in water in a slow rate. -- Abstract: A specially designed cyclic hydrogenated and oxygenated water chemistry in a high temperature aqueous environment was used, and the consequential corrosion behavior of pure Ni was investigated by in situ electric/electrochemical measurements and ex situ surface oxides analyses. The penetrated hydrogen in Ni from the hydrogenated water can enhance oxidation taking place in the subsequent oxygenated water. Ni oxide formed in oxygenated water can be reduced in the following hydrogenated water with a much slower reduction rate than that in gaseous environments. Practical implications of the phenomena in structural materials in nuclear power plants were also discussed.