The Electrochemical Behaviour of 70-30 Cu-Ni Alloy in LiBr Solutions

THE BEHAVIOUR of 70-30Cu-Ni alloy has been investigated in
different concentrations of LiBr solutions from 10-1 to 9 M.
Electrochemical measurements and surface examination complemented
with solution analysis were carried out. The results revealed that the
passivation current of (Ip1) at low anodic potential (-200) is due to
the formation of a doped Cu2O film involving surface enrichment of
nickel. Increasing the anodic potential to ≥ 300 mV, after the
formation of a peak of anodic current maximum (Ip2) a partially
passive film of Cu2(OH)3 Br is formed and the surface suffered from
denicklefication.
Furthermore, solution analysis proves that the alloy dissolves
showing a copper/ nickel ratio in solution which approximation
complete that of the alloy surface . Two types of pitting corrosion
were recorded at 2 and 4 M LiBr, the first one was recorded after Ip1
while the second is recorded after +1000mV. Except the
concentration of 2 and 4 M the first one only of pitting which
recorded after Ip1 were observed beside the general dissolution
through the partially soluble Cu2(OH)3Br.