Reduction of chromate in very low concentration (20 ppm) has been carried out in a GBC reactor. Final concentrations below 0.5 ppm have been achieved at reasonable reaction rates. Spontaneous reduction of chromate by hydrogen in a GBC reactor without an external power source requires careful selection of cathode material. Chemically stable materials such as titanium and RVC tend to passivate when in contact with chromate solution and are unsuitable for use as cathode materials. Graphite, active carbon and graphite felt show no obvious passivation. Reduction of oxidized groups and oxygen are the major side reactions. These occur significantly, especially when using an activated carbon bed as a cathode.