Incorporation of zinc in electroless deposited niclel-phosphorus alloys II. Compositional variations through alloy coating thickness

The zinc state in Ni-Zn-P coatings electrolessly plated from alkaline solut ion with citrate as the main complexing agent was examined by combining X-r ay photoelectron spectroscopy (XPS) and scanning Auger electron spectroscop y (SAES). It was demonstrated that zinc at the surface of Ni-Zn-P films was in an oxidized state. The SAES sputter-etch depth profiling showed that zi nc incorporated within the coating was always accompanied by oxygen with an almost parallel profile, independent of the substrate. Analyzing the obser ved chemical shift of the LMM peaks in SAES and XPS spectra, it seems reaso nable to assume that zinc is incorporated in the coating in a partially oxi dized state. The parallel profiles of all components of the alloy indicated their actual codeposition and suggested almost homogeneous distribution th rough the him thickness in this type of Ni-Zn-P coatings. The elemental pro files in specially designed two-layer samples (Ni-Zn-P over NI-P) demonstra ted the significant reduction in phosphorus content caused by zinc codeposi tion, which started at the interface between Ni-P and Ni-Zn-P. (C) 2001 The Electrochemical Society. All rights reserved.