Surface modification of Inconel-600 by growth of a hydrous oxide film

In this study, Inconel-600 (Ni-Cr-Fe alloy) was modified by repetitive potential cycling in 1 M NaOH solution. This procedure induced the growth of a hydrous oxide film, following the same mechanism as previously reported for pure nickel in alkaline solution under similar experimental conditions. The electrode, modified by 30 repetitive potential cycles, exhibited about one order of magnitude lower current density in both the active and passive ranges of the anodic polarization curve. Selective dissolution of nickel and iron in acid solution was determined by rotating ring-disc electrode measurements. This process resulted in chromium enrichment as shown by use of X-ray electron spectroscopy. The proposed model for the enhanced stability of the modified electrode agrees with the percolation model of passivity of stainless steels and Fe-Cr alloys.