Electrochemical behaviour of copper-nickel alloys in stagnant Na₂CO₃solutions

Abstract

composition of the compounds formed on the alloy surface during the anodic polarisation was characterised using X -ray diVraction analysis. T he dissolution behaviour of the alloy consists of two potential regions separated by the critical potential E crit . T he rst potential region involves the selective dissolution of the more active constituent, nickel, and the appearance of one anodic peak A 1 as a result of the formation of Ni(OH) 2 on the alloy surface. T he second potential region relates to the simultaneous dissolution of copper and nickel. T his region was characterised by the appearance of four anodic peaks A 2 , A 3 , A 4 , and A 5 , which are related to the formation of Cu 2 O, {CuO and Cu( OH) 2 }, CuCO 3 -Cu( OH) 2 composite, and NiOOH, respectively. Potentiostatic current/time transients showed that the formation of Ni(OH) 2 , Cu 2 O, CuO, Cu(OH) 2 , CuCO 3 -Cu(OH) 2 and NiOOH layers involves a nucleation and growth mechanism under diVusion control.