The oxidation of nickel, iron and cobalt foils is followed by measuring the open-circuit potential, and is optically monitored. Intense gas evolution, with particle motion, is found to occur throughout the process. A fundamental explanation is given for the three stages of the oxidation-lithiation process of the nickel electrode. A large window of possibilities for the oxidation of iron is observed. The open-circuit potential evolution of cobalt is similar to that of nickel, due to the similarity of oxidation stages. A very high dissolution and/or disintegration rate under CO2 evolution is observed for metallic cobalt samples. A solid-state based mechanism for the oxygen reduction reaction on NiO is proposed.