Distribution of components of binary nickel—chromium alloys electrodeposited from sulfate—oxalate solutions

Abstract

The composition and distribution of elements over the thickness of electrodeposited nickel—chromium layers are studied by x-ray photoelectron and Auger electron spectroscopy techniques. During a layer-by-layer etching, the Cr : Ni ratio varies with a period of 2–5 nm. This period and the amplitude of the ratio of concentrations of components increases with the current density. During alloy deposition on a copper cathode, the first to deposit is nickel, which exerts a catalytic effect on the chromium deposition, which in turn exerts a catalytic effect on the oxalate reduction to carbon. Once a deposit thicknesses of ~100 nm is reached, the alloy composition becomes constant. The deposits contain considerable amounts of carbon (in the form of graphitized structures and carbides), which increases from 0.6 to 2 wt % with the current density. The surface of the growing alloy 50–70 nm thick is rich in nickel and chromium hydroxides and organic compounds containing carboxyl groups.