Surface treatment for mitigation of hydrogen absorption into alloys

Polarization experiments show that deposited zinc effectively inhibits the discharge of hydrogen up to 46% on AISI 4340 steel, 58% on HY 130 steel, 68% on Inconel 718 alloy, and 60% on Monel K500 alloy compared with the currents obtained on each corresponding bare alloy. In the presence of a monolayer coverage of zinc on the substrates, the hydrogen permeation rate through AISI 4340 steel, HY 130, and Inconel 718 alloy membranes are reduced by 51, 90, 40%, respectively. In the presence of lead, the hydrogen discharge reactions are reduced by 44 and 67% on AISI 4340 steel and Inconel 718 alloy, respectively, and hydrogen permeation through AISI 4340 steel and Inconel 718 membrane are inhibited by 71 and 70%, respectively.; The direct hydrogen entry mechanism was shown experimentally and theoretically to be correct for HY 130 steel and Pd for small values of cathodic current density i{dollar}sb{lcub}rm c{rcub}{dollar}. This mechanism also explains why steady state hydrogen atom permeation current density is independent of the membrane thickness and diffusivity and directly proportional to the cathodic current density. It was found that the direct entry mechanism is applicable only when the rate of hydrogen diffusion through a metal membrane is comparable to the hydrogen absorption rate. This could occur when the hydrogen atom diffusion rate is fast compared to the absorption rate. As a consequence, the absorbed hydrogen immediately diffuses from the anodic side of the metal that has high diffusivity or low thickness and explains why the permeation current density for palladium, iron and iron alloys, is independent of thickness.; In order to interpret the permeation experimental data, the Iyer-Pickering-Zamanzadeh hydrogen permeation model and the direct entry mechanism were modified by including a mass transfer term in the hydrogen discharge equation.