Electroless NiP and NiCuP alloys with high phosphorus content (11 to 13 weight percent) are plated from nonammonia alkaline baths onto aluminum and iron substrates. Energy-dispersive spectroscopy analysis is used to examine the chemical composition of the coatings. Scanning Auger electron spectroscopy is applied to study elemental profiles and the interface with the substrates. The zincate layer transformation at the interface with the aluminum substrate is investigated at two bath temperatures. Nickel, phosphorus, and copper concentration is plotted against the coating thickness to examine the chemical homogeneity and to obtain information about the mechanism of electroless ternary alloy formation on both types of substrates.