Effects of Test Conditions on Corrosion Reactions and Hydrogen Absorption in Hydrogen Embrittlement Tests Using an Ammonium Thiocyanate Solution

摘要

Ammonium thiocyanate is widely used as a reagent for promoting hydrogen absorption by high-strength steels. The effects of the solution concentration, temperature and dissolved oxygen on corrosion film formation, corrosion reactions and hydrogen absorption were investigated in a hydrogen embrittlement test environment using an ammonium thiocyanate aqueous solution. A still bath of a 20 mass% ammonium thiocyanate solution displayed a supply limitation, whereas a solution with flow influenced the corrosion and hydrogen absorption by the tested steel. The concentration of dissolved oxygen that forms an iron oxide film was found to have a small effect on hydrogen absorption. The change in the hydrogen content of the tested steel with elapsed time is explained in terms of changes in the equilibrium concentration of hydrogen on the steel surface and in the corrosion rate. The change in the solution pH during potentiostatic electrolysis tests in an ammonium thiocyanate solution is also discussed.