Cathodic reduction of oxygen on passivated Fe, Ni, Cr and stainless steels in borate solutions

Cathodic reduction of oxygen on stainless steels in neutral or alkaline solutions gives a limiting current. It is known that the limiting current is caused by the chemical reaction control in the oxygen reduction process. Since oxygen reduction occurs on the passive films formed on metals in neutral and alkaline solutions and moreover, the passive films have the semiconductive nature, it is expected that the properties of the passive films strongly affect the oxygen reduction process and probably causes a limiting current. In order to clarify this speculation, the oxygen reduction study was carried out on the passivated Fe, Ni, and Cr from a fundamental aspect. The semiconductive properties of the electrodes was measured by using the ac impeadence technique. It was found out that the pH dependence of the limiting current for oxygen reduction on passivated Fe, Cr, Ni and stainless steels could be interpreted by n-type semiconductive nature of the passive films and that alloying effect of stainless steel on the limiting current density could be interpreted