Electrochemical investigation of hydrogen absorption in a duplex stainless steel Original Research Article

Hydrogen permeation through and hydrogen desorption from duplex stainless steel membranes of various thickness were studied by the electrochemical technique. During the permeation experiments, one side of a membrane was charged with hydrogen by galvanostatic cathodic polarisation in 0.1M NaOH at 25 °C. After an interruption of the hydrogen charging, the desorption rate of hydrogen was measured at both sides of the membrane. The obtained permeation and desorption rates were analysed in terms of the real values of the hydrogen diffusivity (Dα) and the length of diffusion paths (Lα) in the ferrite phase. The total amount of absorbed hydrogen consists mainly of the hydrogen dissolved in the ferrite matrix (diffusible hydrogen) and the hydrogen dissolved in the austenite phase (reversibly trapped hydrogen). Amounts and concentrations of these two forms of hydrogen were evaluated. Some peculiarities and limitations as regards the usefulness of the permeation–desorption measurements for studying hydrogen in the duplex stainless steel membranes are given.