Determination of the hydrogen fugacity during electrolytic charging of steel

This work studied the determination of the hydrogen fugacity during electrolytic charging. With a virgin surface, there were irregular permeation transients, attributed to irreproducible surface conditions. Cathodic pre-charging conditioned the entry side to a stable state. Permeability transients were used to measure the critical parameters in the thermodynamic relationship between hydrogen activity and electrochemical potential. At the same overpotential, the hydrogen fugacity in the pH 12.6 0.1 M NaOH solution was higher than that in the pH 2 0.1 M Na2SO4 solution, attributed to differences in (i) the hydrogen evolution reaction, (ii) the surface state, and (iii) the true surface area. (C) 2014 Elsevier Ltd. All rights reserved.