An electrochemical study of phase-transitions in rust layers

Abstract Isolated rust layers have been investigated by electrochemical methods to find out whether their reduction and re-oxidation can affect the atmospheric corrosion of iron. At potentials below 0 mV, first a thin Fe 2+ -containing surface layer is formed on top of the γ-FeOOH. This reduced surface layer can dissolve into the cell electrolyte at acid pH, or at lower potentials the Fe 2+ -ions can react with γ-FeOOH to Fe 3 O 4 . The formation of magnetite could be followed by in-situ magnetic measurements. The reduced surface layer can easily be oxidized back to γ-FeOOH, magnetite can partly be oxidized to γ-Fe 2 O 3 .

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