Oxide Film Growth on Copper in Neutral Aqueous Solutions

Abstract

The copper electrode potentials measured by the open circuit potential method in strongly aerated solutions of SO₄^-2, Cl^-, Br^-, I^-, CrO₄^-2, CO₃^-2, and NO₂^- with difference concentrations, till steady state values are attained. The copper electrode potentials of the all experiments increase from negative to more positive values indicating oxide film growth. The copper oxide film thickness attains maximum value at low and high concentrations of each aggressive and inhibitive anions respectively. The rate of oxide film thickening is determined by use the relation: E = a + b log t, where a and b are constants. The concentration of the inhibitive anions, CrO₄^-2, CO₃^-2, and NO₂^- that can withstand a certain concentration of the aggressive ions, , Cl^-, Br^-, and I^-, varies due to the relation: logC _inh. = A + n logC _agg., where A and n are constants. The all experiments were investigated at 25^oC in all electrolytes.

Keywords: Copper; oxide growth; passivity; open circuit potential.