An investigation was made of the effect of hydrostatic pressures upon the permeation and diffusion of H in Armco Fe (table 19). A diffusion gradient was imposed on an Fe foil by producing H cathodically on one side of the foil, with the simultaneous removal of H from the opposite side via an electrochemical anodic reaction which oxidized the H to give water. The resultant current, due to the H oxidation reaction, was measured and was related to the H permeation rate. The results showed that a hydrostatic pressure increased the residual H permeation rate in a linear manner up to about 6000psi. A marked increase in the permeation rate then occurred between 6000 and 8000psi. The pressure effects upon H permeation were reversible between 0 and 8250psi. Hydrostatic pressures of up to 6200psi did not affect the diffusion coefficient of H. The absence of a hydrostatic pressure effect upon the Fe diffusion coefficient indicated the existence of minimal lattice distortion.

J.J.DeLuccia: Clearing House for Federal Scientific and Technical Information, Report AD667596

Table 19

Diffusivity of H in Fe at 21C under Hydrostatic Pressure