Stress corrosion cracking and hydrogen diffusion in magnesium

Evaluation of the stress corrosion cracking (SCC) of magnesium (MG) showed that the mechanism of Mg SCC involves mostly hydrogen (H). Mechanical or chemical rupture of a partially protective film allows aqueous solution access to the Mg metal and H is liberated as the catholic partial reaction of the Mg corrosion. Ce in the hybrid sample of a Mg-Ce alloy reacted with H to form hydrides. Permeation experiments were conducted where Pd over-layer was deposited on both sides as an H catalyst using pure H2 gas as the charging medium. H permeation was measured with a calibrated vacuum gauge on the exit side of the membrane maintained at a pressure of -10-7 Pa. The H diffusion coefficient from molecular dynamics simulations was estimated and the value of the H diffusion coefficient sufficient to allow H transport ahead of a stress corrosion crack in Mg at ambient temperature is determined.