XPS Study of the Segregation of Minor Elements at the Surface of a Commercial Copper-10 wt.% Nickel Alloy

X-ray photoelectron spectroscopy has been used to examine the effects of industrial reduction treatments on the composition and structure of the topmost layers of a commercial copper–10 wt.% nickel alloy (Cu–10Ni). The surface analytical studies carried out on the as-received alloy show, in addition to the usual surface contamination, the formation of nickel(II) hydrated species and pronounced segregations of additive alloying components. Strong enrichments of minor elements are also observed in the outermost layers of the material. Moreover, metallic copper and nickel-based compounds are homogeneously distributed within the segregants in the surface film. Comparison of the surface composition of samples treated in various controlled-reducing atmospheres with a mechanically cleaned alloy surface gives access to the mechanisms responsible for the segregations. The diffusion of the various chemical species is discussed in terms of oxygen potential, leading to concentration gradients of metallic elements. © 1997 by John Wiley & Sons, Ltd.