INFLUENCE OF TEMPERATURE AND HYDROSTATIC PRESSURE ON HYDROGEN DIFFUSIVITY AND PERMEABILITY IN 13% Cr SUPER MARTENSITIC STAINLESS STEEL UNDER CATHODIC PROTECTION

New equipment has been developed to study hydrogen diffusion in metals at different temperatures, mechanical loads and hydrostatic pressures. The hydrogen permeation measurement method is based on the electrochemical hydrogen permeation technique developed by Devanathan and Stachurski. The paper presents equipment design, capabilities and limitations. Hydrogen diffusivity and permeability in 13%Cr super martensitic stainless steel was studied at 20, 50 and 80ºC and at atmospheric and 100 bar  hydrostatic pressure. The effective hydrogen diffusion coefficient increased with temperature according to the Arrhenius equation. Application of 100 bar hydrostatic pressure at 80ºC did not influence the hydrogen concentration in the test material relative to that obtained at atmospheric pressure.