Depth profiling studies of oxidized alloy surfaces by glow discharge emission spectroscopy

Depth profile analyses of elemental composition of Cu–Ni and Fe–Cr binary alloys oxidized in air and O 2 gas mixtures were performed by glow discharge emission spectroscopy (GDS), adopting the cathode sputtering technique with a Grimm‐type glow lamp. The emission intensity ratio of Cu I 327.4/Ni I 352.5 for the oxidized Cu–Ni alloys is much larger than that for the non‐oxidized alloy at the beginning of the discharge, because of copper segregation on the surface of the oxidized Cu–Ni alloys. The composition depth profile analysis for oxidized Fe–Cr binary alloys indicates the presence of a stable chromium oxide formed on the surface, particularly a thinner oxide film for alloys having higher chromium concentration. The discharge current for the non‐oxidized alloy is almost constant during sputtering, but grows smaller for the oxidized alloys. This discharge behaviour must be considered in quantification.