Abstract
The analytical and potentiometric study (using an Ag/Ag+ reference electrode) of the behaviour of pure iron in molten sodium metaphosphate at 750°C shows that a non-polarized electrode corrodes: iron is oxidized to soluble Fe2+ ions and, simultaneously, an Fe2P and FeP2 deposit resulting from phosphate anion reduction is formed on the electrode surface.
The variations of the mixed potential and of the total mass of oxidized iron show that the corrosion rate decreases as the immersion time increases. Such an inhibition comes from the gradual coating of the electrode surface with the iron phosphides: the corrosion rate is controlled by the iron diffusion through the deposit, the thickness of which increases with time.
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Belcadi, S., Rameau, J.J. & Barbier, M.J. Corrosion of pure iron in fused sodium methaphosphate. J Appl Electrochem 3, 185–191 (1973). https://doi.org/10.1007/BF00619160
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DOI: https://doi.org/10.1007/BF00619160