Electrochemical characterization of nano zinc ferrite coating on carbon steel by pulsed laser deposition

Abstract

The structural materials in water-cooled nuclear power reactors are mainly iron and nickel based alloys. Continuous operation of these nuclear reactors at high temperature and high pressure aqueous environment leads to the formation of various oxides due to corrosion of the structural materials. Since the corrosion process is mainly interfacial and electrochemical in nature, the interfaces formed between the alloys/oxide and oxide/solution plays a crucial role in deciding the overall corrosion resistance of the structural materials. In this context, efforts are being made to modify the size of the oxide particles (surface morphology) to nano size and/or change the composition of the oxides by the addition of an external metal ion (Metal Ion Passivation) both of which are likely to improve the adherence and protectiveness of the interfacial film. In this paper, attempts were made to form an additional nano zinc ferrite (ZnFe2O4) coating by pulsed laser deposition technique on the magnetite (Fe3O4) layer formed on carbon steel for improving the corrosion resistance of the base metal. The ZnFe2O4 was synthesized by co-precipitation method and its phase purity was confirmed by Raman Spectroscopy and X-Ray Diffraction studies. 10mm diameter ferrite targets were prepared and a thin film of ZnFe2O4 was deposited on the Fe3O4 coated carbon steel specimens using pulsed laser deposition technique. Characterization of this deposited ferrite film was carried out by Raman spectroscopy, X-Ray Diffraction, X-ray Photoelectron Spectroscopy and Secondary Electron Microscopy. The semiconductor properties of these oxides were investigated by Mott-Schottky plots. The mechanism of corrosion resistance/improvement in the deposited layer was studied by electrochemical techniques and the results are presented in detail in this paper.