Permeation of hydrogen through fe during cathodic polarization under hydrostatic pressure

The effect of pressure on hydrogen entry into steel has been investigated by studying the rate of permeation of hydrogen through a thin Fe diaphragm. The results indicate that as the pressure increases the surface coverage of hydrogen atoms, which determines the rate of hydrogen permeation, becomes increasingly controlled by the rate of diffusion of hydrogen dissolved in the aqueous solution. Above 250 atm. the linear increase in the permeation rate appears to be due to the effect of pressure on the state of hydrogen segregated at voids in the metal. The work is of significance in relation to the cathodic protection of steel structures immersed at depth in the sea.