• Małkiewicz, Konrad
• Wierzchoń, Tadeusz
• Rębiś, Janusz
• Kamiński, Janusz

Abstract

<p>The paper presents comparative results of corrosion resistance tests on AISI304 steel orthodontic arch-wires, before and after low temperature plasma nitriding or oxynitriding, carried out at cathodic potential. Oxynitriding processes were carried out at different concentrations of air added. Corrosion resistance tests of diffusion surface layers were carried out via electrochemical impedance spectroscopy and the po-tentiodynamic method in non-deaerated artificial saliva solution at 37 °C. The results were complemented with analysis of the alloy’s structure and surface topography. They showed an increase in corrosion resistance of AISI304 steel after glow-discharge nitriding and ox-ynitriding. In addition, due to the considerable roughness of the initial material, the surface layers produced are susceptible to pitting corro-sion. Increasing the concentration of air in a reactive atmosphere neg-atively affects the electrochemical homogeneity of the layer, which is not translated, due to the low concentration of chlorides in corrosion environment, to reducing the durability of the produced layers. This is evident in the values of breakdown potential (E_np) initiating pitting corrosion, which are comparable in all cases and amount to approx. 820 mV ± 30 mV, slightly exceeding (by approx. 100 mV) the breakdown potential of the initial material. Only in the case of the layer with the maximum oxygen addition, the presence of a transpassive area is observed within which the oxynitrided layer is redeveloped, resulting in the observed exfoliation process of the layer.</p>

Topics

• impedance spectroscopy
• surface
• stainless steel
• Oxygen
• reactive
• pitting corrosion
• durability
• wire