Evaluation of corrosion resistance of nano nickel ferrite and magnetite double layer coatings on carbon steel

The major structural material employed in the primary coolant system of pressurized heavy water reactors is carbon steel. The formation of corrosion products on the structural material surfaces, transportation to the core by the coolant and deposition of activated corrosion products on the out-of-core surfaces are controlled by several factors. Magnetite is the major corrosion product formed on carbon steel. The nickel released from other structural materials viz., nickel based steam generator tubes, partially converts the magnetite to nickel ferrite. These oxides, if modified to nano size, could improve the protectiveness of the interfacial film. Nickel ferrite synthesized by co-precipitation method was deposited on magnetite coated carbon steel by pulsed laser deposition technique and characterized by laser Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The results showed that the deposited nickel ferrite film was nanocrystalline and in single phase. The corrosion resistance and the electronic properties of the deposited film were evaluated by electrochemical techniques and the results are discussed in this paper.