The influence of surface microstructure and chemical composition on the corrosion behavior of AISI 1045 (UNS G10450) plain steel modified by plasma-assisted diffusion of nitrogen and oxygen was investigated. A detailed surface characterization was performed before and after cyclic potentiodynamic polarization and salt spray tests, using scanning electron microscopy at low and high resolutions, energy-dispersive x-ray spectroscopy, x-ray diffraction, and glow discharge optical emission spectroscopy. The corrosion resistance as determined by cyclic potentiodynamic polarization was found to depend more strongly on the morphology and composition of the outermost oxynitride layer than on its thickness. For post-oxidation times below and above 90 min, the oxynitride layer presented defects that can act as pathways for corrosive species. The degradation of the corrosion resistance for longer processing times is through cracking of granules, which were previously formed at shorter times owing to the hydrogen accumulation at the oxide-nitride interface. The salt spray tests revealed a main dependence on the manganese sulfide (MnS) inclusions content in the base material.

Subject
Scanning electron microscopy, Steel surfaces, Oxide layers, Iron, Plasma, Constants, Nitrogen, Salt spray corrosion testing, Steel, Corrosion resistance, Nitriding, Inclusions, Samples
Keywords:
corrosion resistance, inclusion, plasma treatments, steel, surface microstructure
© 2014 NACE International
2014
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