Copper–nickel alloys modified with thin surface films: Corrosion behaviour in the presence of chloride ions

► Influence of the Ni content on the corrosion resistivity of Cu–Ni alloys. ► Corrosion investigation using ac and dc methods in stagnant and flow conditions. ► Inhibiting efficiency of bis(diethyldithiocarbamato)Cu/Ni complexes. ► Solid state properties of spontaneously formed and inhibitor surface films. ► Ni 2+ ions segregation, solid-state processes within the surface films. A strong influence of the Ni content in on the barrier properties of the surface films, spontaneously formed on Cu–Ni alloys (containing 10–40 at.% of Ni) in a slightly alkaline NaCl solution or previously produced by forming bis(diethyldithiocarbamato)Cu(II) and Ni(II) surface complexes, were studied under stagnant and solution impinging conditions using polarization and EIS methods. An unexpected behaviour that the corrosion resistivity of alloys with x(Ni) ⩾ 20 at.% is lower than that of the Cu–10Ni alloy was explained using solid-state processes within the surface films and enhanced electronic conductivity of the surface film formed on the Cu–10Ni alloy.