| Hydrogen is one of the most abundant elements in nature, it plays an important role in the chemical, petroleum, energy and other industries, and hydrogen extraction and processing are essential for global economic development. However, when hydrogen enters into the metal structure material, it will cause the material mechanical properties such as toughness and ductility decreased, leading to hydrogen-induced material damage. In order to avoid or delay the damage of hydrogen on metal materials, one or more layers of hydrogen barrier coatings are commonly prepared on metal materials surface to impede or delay the entry of hydrogen. Therefore, the investigations of permeation behavior of hydrogen in metallic materials play an important role in improving the hydrogen damage theory of metallic materials, furthermore, in order to prevent hydrogen corrosion, research on hydrogen resistance coatings is significant for enhancing the service life of critical hydrogen equipment.In this dissertation, AISI304austenitic stainless steel was used as a research object firstly, hydrogen permeation behaviour in austenitic stainless steels were investigated by the electrochemical hydrogen permeation technique, the effect of different cathodic current densities on the effective diffusion coefficient, and the hydrogen concentration beneath the cathodic surface and the steady state permeation current density were analysed. Cathodic hydrogen charging method and X-ray diffraction analysis were utilized to investigate the effect of cathodic hydrogen charging and aging after cathodic hydrogen charging on phase transformation in both cold-rolled and annealed AISI304stainless steels, and the effect of hydrogen charging and aging on surface cracking.Low carbon steel was used as substrate material to study hydrogen barrier mechanism of hydrogen resistance coatings, which has a larger diffusion coefficient. The effective diffusion coefficient of hydrogen in the low carbon steel was determined by means of hydrogen diffusion theory fitting method and the time lag method, the diffusion coefficient and the concentration distribution of hydrogen in the low carbon steel were analyzed by the partial decay and build-up transients fitting.By adjusting the composition ratio of plating solutions and plating process parameters, Zn-Ni-Cd ternary alloy plating was obtained. By means of pure iron foil were used as substrate, the hydrogen diffusion coefficient and the apparent solubility of Zn-Ni-Cd ternary alloy were obtained. Permeation behaviors between low carbon steel and low carbon steel combinatorial material with different Zn-Ni-Cd plating thickness were compared under the same cathodic hydrogen charging, and the effect of Zn-Ni-Cd plating on hydrogen permeation resistance was analyzed. The double desorption current density curve at the entry and exit side after hydrogen diffusion achieving steady state was used to determine the contents of diffusible and trapped hydrogen in the low carbon steel and combinatorial material with Zn-Ni-Cd plating, and the effect of trapped hydrogen on hydrogen permeation resistance in combinatorial material with plating was discussed.By assuming that hydrogen concentration distribution in each layers meet Henry’s law, the join conditions of hydrogen diffusion at the interface between the two layers of material were established, and one-dimensional diffusion model in the combinatorial coating/metal specimens was established by using the Fick second law. According to the relevant experimental parameters of hydrogen diffusion through the combinatorial specimens with a Zn-Ni-Cd plating, hydrogen concentration distribution as a function of time and specimens thickness in the every layer of the specimens, permeation current density variation at the anode side and the corresponding hydrogen barrier effect and mechanism were discussed in detail. |
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