Hydrogen permeation through iron

Iron and Steel Hydrogen permeation through iron and steel membranes has been investigated extensively. The assumption has usually been made that, as with palladium, a constant... 

Beck, et al. have used the permeation technique to study the effect of uniaxial tensile stresses in the elastic region on hydrogen permeation through pure iron, and have shown that it increases with increase in stress. The partial molar volume of hydrogen (cubic centimetres of hydrogen per mole of iron) in ferrous alloys can be evaluated from the variation of permeation with applied stress, and from the relationship... 

HG Nelson and JE Stein, Gas-phase Hydrogen Permeation Through Alpha Iron, 4130 Steel, and 304 Stainless Steel from less than 100°C to near 600°C (NASA TN D-7265), Ames Research Center, National Aeronautics and Space Administration, Moffett Field, CA, April 1973. 

D.H. Coleman, G. Zheng, B.N. Popov, R.E. White, The effects of multiple electroplated zinc layers on the inhibition of hydrogen permeation through an iron membrane, J. Electrochem. Soc. 143 (1996) 1871-1874. 

Figure 1-50. Measurements of hydrogen permeation through metal (iron) with two coupled electrochemical cells and a common metal membrane according to Bockris and Devanathan (Bockris and Reddy, 1977 Bockris and Devanathan, 1957). CE counter electrode, RE reference electrode the iron membrane is the working electrode for both cells with cathodic reduction on the left and hydrogen oxidation on the right.

A linear dependence of on often used as evidence for diffusion control in hydrogen permeation through an iron membrane. Such a test is valid for uncoated iron, provided that the equilibrium condition at the input surface is satisfied. However, this test has also been applied to iron coated with palladium on the input surface. Since hydrogen evolution on palladium involves fast discharge followed by slow recombination, can be proportional to 4 or for palladium, depending on whether adsorption occurs under Langmuir or Temkin conditions. Moreover, the assumption of equilibrium at the input surface may... 

The content of this chapter is closely related to permeation, which is the transport of a solute across a layer of solvent (or membrane) under the action of a difference in activity. For example, the permeation of hydrogen through a metal foil has been studied, particularly for palladium [F.A. Lewis (1967)] and iron [J. P. Hirth (1980) H. H. Johnson (1988)]. One reason for studying the permeation of hydrogen through iron is to understand the hydrogen embrittlement of steel. 

S. Chatteqee, B.G. Ateya, H.W. Pickering, Effect of electrodeposited metals on the permeation of hydrogen through iron membranes, MetaH. Trans. A 9 (1978) 389-395. 

Industrially, the above reaction is conducted at atmospheric pressure and at 800-900 C with nickel or iron catalysts. The hydrogen-rich gas mixture (i.e., 75 vol.% and 25 vol.% N ) that contains only traces of unreacted ammonia can be used as-is or purified by pressure swing absorption, or gas permeation through Pd-Ag membrane. 

The influence of temperature upon the permeation velocity of hydrogen through iron and through palladium (53) shows that the rate of flow rises exponentially with the temperature The slope of the curves log (permeability) against 1/T(T = K.) for the Hg-Fe system (Fig. 71) is the same at all current densities from 0-0075 to 0-045 amp./cm., and is very nearly that found for the thermal j)ermeability ( eiect. = caL/atom,... 

This equilibrium is of importance in providing diagnostic criteria for the mechanism of the h.e.r., since the rate of permeation of hydrogen through a thin iron membrane can provide information on the coverage of the surface with adsorbed hydrogen. 

The permeation of hydrogen through an iron diaphragm is illustrated in Fig. 20.20 for the sequence of events... 

Fig. 20.20 Permeation of hydrogen through a thin iron membrane...

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