Enhancement in corrosion resistance of austenitic stainless steels by surface alloying with nitrogen and carbon

In this work, attempts have been made to alloy the surfaces of austenitic stainless steels simultaneously with nitrogen and carbon in the glow discharge of a plasma at temperatures below 450 degrees C. As a result of such a low temperature hybrid treatment, a dual-layer structure is produced, which comprises a nitrogen-enriched layer on top of a carbon enriched layer. Both nitrogen and carbon are supersaturated in the austenitic face-centred cubic structure in the respective sublayer. Electrochemical corrosion tests have been conducted potentiostatically in a 3 wt.% NaCl aqueous solution to measure the anodic polarisation curves of the alloyed surfaces. The results show that this hybrid treatment can significantly improve the corrosion resistance of austenitic stainless steels by several orders of magnitude over a wide range of potentials. (C) 2005 Elsevier B.V. All rights reserved.