XPS characterization of the corrosion film formed on the electroless nickel deposit prepared using different stabilizers in NaCl solution

X-ray photoelectron spectroscopy (XPS) was used to examine the corrosion films formed on electroless nickel (EN) deposits prepared in an EN solution containing two different types and concentrations of bath stabilizers in Ar-purged and oxygenated neutral 5% NaCl solution. Two distinctive corrosion films were observed after long periods of immersion. An enrichment of elemental phosphorus compared to nickel was observed on the surface of the EN deposit produced with no stabilizer and with maleic acid (MA). By comparison, a high degree of surface oxidation was observed on the EN deposit prepared with thiourea. Trace impurities of sulfur in the EN deposit prepared with thiourea appear to result in enhanced corrosion and, in turn, lead to the build-up of corrosion products on the EN surface. By contrast, a P-enriched chemical passivation layer was formed on the EN deposits prepared either without any stabilizer or with MA present. Copyright (c) 2007 Crown in the right of Canada, and John Wiley & Sons, Ltd.