Corrosion Behaviour of Ni in Aprotic Solvents an Electrochemical, XPS and AFM Study

Electrochemical and X-ray photoelectron spectroscopic (X.P.S.) techniques have been used to study the passivation of nickel in 0.1 M H 2 SO 4 DMF and ACN solutions with different water content. Electrochemical results indicate the anodic formation of a thin, poor protective layer and the possibility of salt precipitation onto the metallic surface. A.R.X.P.S. results indicate that while in the anodic film formed in DMF, Ni(OH) 2 constitute the superficial component under which a discontinuous layer of NiO and NiSO 4 is present. Ni(OH) 2 and NiSO 4 are the more superficial constituents in the passivation layer formed in ACN, while NiO becomes prevalent in the underlying layers. A.F.M. images show that in both the solvents the sample surface is very dishomogeneous with flakes and fractures.