Oxygen dissolved in seawater is the source of severe corrosion issues in off-shore platforms for oil exploitation. The electrocatalytic reduction of dissolved oxygen from seawater was investigated at laboratory scale as an alternative to the current processes for the removal of oxygen. Due to the low concentration of dissolved oxygen and the very high conversion required before use of seawater in off-shore platforms, the reduction has been carried out in a packed bed electrode consisting of carbon-based particles of various nature. The reduction involves the intermediate formation of peroxide species whose further reduction into hydroxyl ion is a slow process on Pt-free surfaces. A continuous laboratory packed-bed electrode was designed and tested in long-term operations for the assessment of the production and the reaction selectivity. The removal of oxygen from seawater can be inhibited by the formation of a solid CaCO3-Mg(OH)(2) film at the carbon particles, which favours the accumulation of peroxide species. However, this electrode deactivation can be avoided at sufficient polarisation.