Aqueous and atmospheric corrosion of cobalt-nickel alloys

Abstract

The corrosion of cobalt-nickel alloys at ambient temperatures is reviewed. In the aqueous phase, data for the anodic and cathodic half-cell reactions are reported, as also for free corrosion. Under most conditions, corrosion resistance increases with nickel content, although in certain circumstances, the 50–50 wt-% alloy is found most resistant. The involvement of catalytically active spinel structured double oxides is apparently important at this composition. Under atmospheric corrosion conditions, such little evidence as exists suggests that cobalt decreases corrosion resistance. The (mainly patent) literature relating to corrosion inhibitors for atmospheric use is reviewed. The growing importance of these alloys in the context of the new generation of METs (metal evaporated tapes) and experimental problems in the corrosion study of such tapes are discussed.