THE DETERMINATION OF EXPERIMENTAL PARAMETERS NECESSARY FOR THE MODELING OF HYDROGEN EMBRITTLEMENT OR STRESS-CORROSION CRACKING USING THE ELECTROCHEMICAL PERMEATION TECHNIQUE

The knowledge of the diffusion coefficient of hydrogen in metals and t he related problems of surface effects, trapping and short path for hy drogen diffusion is necessary for the understanding of hydrogen embrit tlement and stress corrosion cracking phenomena, This paper presents t he capabilities of the electrochemical permeation technique to get qua ntitative information on the effect of surface effects (passive, oxide or corrosion films), deformation or grain boundaries on the hydrogen diffusion and permeability to hydrogen of iron, ferritic steels and ni ckel, These factors may govern the diffusion process as well as the el ectrochemical conditions, leading to a wide range of data for hydrogen diffusivity. They must be taken into account in the analysis of embri ttling phenomena where hydrogen is supposed to be involved.