Sensors for Corrosion Detection: Measurement of Copper Ions in 3.5% Sodium Chloride Using Screen-Printed Platinum Electrodes

Planar screen-printed platinum electrodes developed for use in corrosion monitoring have been evaluated using cyclic differential pulse voltammetry and shown to detect cupric ions (Cu
²⁺
) over a range up to 100 mM in a background of 3.5% by weight sodium chloride solution. The reduction of Cu
²⁺
to metallic copper is shown to proceed as two successive single-electron transfer reactions involving an intermediate chemical step where the cuprous ion (Cu
⁺
) is complexed by chloride to form the dichlorocuprous anion CuCl
₂
^-
. By comparison, the complexation step during the oxidation of copper to Cu
²⁺
can involve a number of different chlorocopper(I) complexes of the general form [CuCl
_(n+1)
]
^n-
depending on the chloride concentration, which can make detection via a stripping reaction difficult.