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 (Cu²⁺) over a range up to 100 mM in a background of 3.5% by weight sodium chloride solution. The reduction of Cu²⁺ 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 CuCl₂^-. By comparison, the complexation step during the oxidation of copper to Cu²⁺ 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.