A study was made of the diffusion of H in by using electrochemical measurements involving a time-breakthrough method, as well as by measuring the H uptake in a Sieverts-type apparatus at constant pressure. The latter technique involved monitoring changes in the volume of the gas. Data were determined for a series of randomly substituted face-centered cubic Au-Pd alloys, at 0 to 112C, for small H contents; where the dissolved H behaved ideally. A Au content of about 20atom% had little effect upon the diffusion efficient. That is, it was unchanged from that for pure Pd. At Au contents which were greater than 20%, the diffusivity declined logarithmically - with the Au content - to a value of 7.4 x 10-10cm2/s at 37C for the 55.7%Pd alloy (table 13). Typical results could be described by:

44.7at%Au:     D (cm2/s) = 6 x 10-4 exp[-7.26(kcal/mol)/RT]

55.7at%Au:     D (cm2/s) = 4.8 x 10-4 exp[-8.68(kcal/mol)/RT]

S.Maestas, T.B.Flanagan: Journal of Physical Chemistry, 1973, 77[6], 850-4

Table 13

Diffusivity of H in Au-Pd at 37C