Surface analysis of Ni/Al alloys by X-ray photoelectron spectroscopy

The surface composition of various pretreated NiAl alloys was investigated by the XPS method. Surface enrichment of Al is observed in freshly polished samples. Storage in air (or H₂O), especially at elevated temperatures, greatly increases the thickness of the aluminium oxide (or aluminium hydroxide) layer and reduces the nickel intensities correspondingly. Treatment with NaOH dissolves aluminium out of the surface, which is thus left with a high nickel content. The changes in this surface caused by exposure in air and H₂O are observed.