Electrochemical behaviour of synthetic 90/10 Cu–Ni alloy containing alloying additions in marine environment

Abstract

The effect of alloying elements including aluminium, chromium, cobalt, indium, molybdenum, titanium and vanadium on the corrosion behaviour of a synthetic 90/10 Cu–Ni alloy in natural sea water and in artificial saline solutions (containing 2·86 wt-%NaCl and 0 or 2260 ppm sulphate) was investigated. Synthetic alloys were prepared in an induction furnace, under an Ar/7 vol.-%H₂ atmosphere in cylindrical boron nitride crucibles and were heat treated in a tube furnace. The electrochemical measurements were conducted using aerated electrolytes at room temperature using a potential range between −1·5 and +2·5 V(SCE). Tafel extrapolation, cyclic polarisation, cyclic voltammetry and linear polarisation electrochemical techniques were applied in this investigation. It was concluded that the corrosion behaviour of the synthetic alloys depends on the alloying element added to the alloy. Cobalt was detected to be the most effective alloying element and aluminium may be used as an alloying element only in the absence of sulphate. Chromium could be used to some extent while the use of molybdenum, indium, vanadium or titanium as alloying elements did not improve the corrosion properties of 90/10 Cu–Ni alloy.