PROCESSING AND ELECTROCHEMICAL CORROSION RESISTANCE OF A NANOCRYSTALLINE Fe-20Cr ALLOY

摘要

Discs of nanocrystalline (nc) and microcrystalline (mc) Fe-20Cr alloys were prepared by high energy ball milling followed by pre-annealing, compaction and sintering. Electrochemical corrosion of discs of nc and mc Fe-20Cr alloys thus produced was investigated at room temperature in 0.5M H_2SO_4 solution using potentiodynamic polarization tests. Nanocrystalline Fe-20Cr alloy has shown improved electrochemical corrosion resistance over its microcrystalline counterpart as characterized by passivation potential, critical current density and passive current density. Passivation is achieved at relatively lower potential in nanocrystalline form of alloy. Compositional characterization of passive films carried out by X-ray photoelectron spectroscopy (XPS) suggests higher Cr content in the passive film of nanocrystalline form of the alloy than that of their microcrystalline counterpart. Based on the XPS and polarization results, mechanistic understanding of the observed enhancement in the corrosion resistance of the nanocrystalline Fe-Cr alloys is discussed.