Oxygen Reduction Reaction

Definition

The oxygen reduction reaction is the dominant cathodic half-reaction in aerated water systems, O2 plus 2H2O plus 4e- giving 4OH-. It consumes electrons and generates hydroxide.

Oxygen exists as a stable covalent molecule but is an exceptionally strong electron sink, so its reduction sustains the corrosion current by consuming the electrons released at the anode. The reaction raises pH locally by producing hydroxide ions, which can shift carbonate equilibria at the surface. Because oxygen drives this reaction, removing or excluding oxygen weakens the entire circuit.

Related concepts

Cathode · Cathodic Control · Oxygen Differential Corrosion

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Part of The Blueprint of Water · ⚡ electrochemistry