The effect of lattice defects and microstructures upon the H distribution in pure Al, and in Al-based alloys, was studied by means of T electron micro-auto-radiography. It was found that, in the pure Al and in both of the alloys, dislocations and grain boundaries acted as short-circuit diffusion paths and also as trapping sites for H. It was noted that the Guinier-Preston zones in the Al-Mg2Si alloy did not act as trapping sites but as repellers of H, in contrast to the Guinier-Preston zones in the Al-Cu alloy; in which they acted as trapping sites for H. In the Al-Mg2Si alloy, the interfaces between the matrix lattice and the metastable ’ precipitates and between the matrix lattice and the equilibrium  precipitates, were strong trapping sites for H. In the case of the Al-Cu alloy, the equilibrium  precipitate itself was able to trap H.

H.Saitoh, Y.Iijima, K.Hirano: Journal of Materials Science, 1994, 29[21], 5739-44