Stability of electrochemical hydrogen charging in NaCl aqueous solution containing NH4SCN: Effect of changes in solution chemistry

Stability of electrochemical hydrogen charging to iron during potentiostatic polarization in a 3 wt.% NaCl aqueous solution containing NH 4 SCN was investigated using electrochemical hydrogen permeation tests. The hydrogen absorption rate remained stable when the specimen was polarized at potentials of −0.9 V (vs. Ag/AgCl (3.33 M KCl)), −1.1 V, or −1.3 V. However, at polarization potential of −1.6 V, the hydrogen absorption rate fluctuated considerably over time. This fluctuation was attributed to changes in solution chemistry, where the proton concentration increased and the SCN – concentration decreased because of the oxidation reaction of SCN – on the Pt counter electrode. • Hydrogen absorption rate was stable at the polarization potential of −0.9 to −1.3 V. • Hydrogen absorption rate was fluctuated over time at the polarization potential of −1.6 V. • The fluctuation was attributed to changes in solution chemistry.