Cathodic Reduction Model of Copper Oxides Films Formed in Presence of Acetic Acid

A cathodic reduction model of oxide films formed on copper in presence of acetic acid has been proposed. The simulation is based on copper oxides obtained during 21 days in climatic chamber experiments with 0, 500 and 800 ppb of acetic acid at 95% RH. It was found that as the concentration of the acid increases, the formation of the copper oxide (I) increases. The cathodic reduction was carried out in 0.1M KCl until hydrogen evolution indicating the end of the reduction. The curves were modeled taking into account the electrochemical reduction of copper (II) oxide (CuO), amorphous cuprite (Cu₂O)_am, intermediate cuprite (Cu₂O)_in, crystalline cuprite (Cu₂O)_cr, and hydrogen. These oxides have been previously detected in similar conditions and are considered to follow the Langmuir isotherm. No evidence of copper carboxylate was found by the electrochemical method. The result shows a relative accuracy of 0.98 or better in R2 coefficient.

Keywords: Cathodic reduction, atmospheric corrosion, copper, acetic acid.