Electrochemical and XPS studies of the corrosion behavior of sputter-deposited amorphous Fe–Cr–Ni–Nb alloys in 6 M HCl

Abstract

Amorphous Fe–Cr–Ni–Nb alloys containing 9–68 at.% niobium were successfully prepared by the D.C. magnetron sputtering method using targets consisting of a commercial Type 304 stainless steel disc and high purity niobium discs. The corrosion rate of the sputter-deposited Fe–Cr–Ni–Nb alloys containing more than 19 at.% niobium in 6 M HCl at 30°C was more than four orders of magnitude lower than that of bulk Type 304 stainless steel and almost the same as that of sputter-deposited niobium metal, although the corrosion rate of the alloys was higher than that of the binary Cr–Nb alloys. The corrosion potential of the alloys was higher than that of niobium and all the Fe–Cr–Ni–Nb alloys were spontaneously passivated in 6 M HCl at 30°C. XPS analysis revealed that the spontaneous passive films formed on the alloys after immersion in 6 M HCl for 48 h were rich in chromium and niobium cations and deficient in iron cation. The formation of the homogeneous double oxyhydroxide films containing chromium, niobium and iron cations is responsible for the high corrosion resistance of the alloys.