This study focuses on how different electrolyte parameters of the chlorate process affect the cathode potential for hydrogen evolution on iron in a wide current-density range. The varied parameters were pH, temperature, mass transport conditions and the ionic concentrations of chloride, chlorate, chromate and hypochlorite. At lower current densities, where cathodic protection of the electrode material is important, the pH buffering capacity of the electrolyte influenced the potential to a large extent. It could be concluded that none of the electrolyte parameters had any major effects (<50 mV) on the chlorate-cathode potential at industrially relevant current densities (around 3 kA m⁻²). Certainly, there is more voltage to gain from changing the cathode material than from modifying the electrolyte composition. This is exemplified by experiments on steel corroded from operation in a chlorate plant, which exhibits significantly higher activity for hydrogen evolution than polished steel or iron.