Preparation and hydrogen barrier mechanism of Ni-based coatings on X80 pipeline steel

Ni, Ni-Zn, and Ni-Zn-P coatings were electrodeposited on the surface of X80 pipeline steel to explore their hydrogen barrier behavior. Hydrogen adsorption and desorption as well as the absorption and diffusion process were investigated by experiments with Devanathan-Stachurski double electrolytic cell and electrochemical impedance spectroscopy (EIS), and the kinetic parameters of hydrogen permeation were estimated via modelling and data fitting. Furthermore, the distribution, hydrogen concentrations and corresponding binding energies of different hydrogen traps in the coatings and at the coating/substrate interface were measured by the glow discharge optical emission spectroscopy (GDOES) and thermal desorption spectrum (TDS). Although hydrogen is more likely to be produced and accumulated on the surface of Ni-based coatings than that of the bare X80 steel, it is confirmed that amorphous Ni-Zn and Ni-Zn-P coatings can effectively reduce the apparent hydrogen diffusion coefficient of the coated sample, with Ni-Zn-P exhibiting more pronounced effect. This is mainly attributed to the high concentration of reversible hydrogen traps at the coating and coating/substrate interface.