Polarization of Copper in Acidic and Alkaline Solutions

The polarization behavior of copper in acidic and alkaline solutions has been investigated. The cathodic Tafel slopes of copper in acidic solutions for hydrogen evolution by discharge of hydrogen ions were approximately 112 mv. The electrochemical reaction order for this reaction with respect to the concentration of hydrogen ions was one-half. For alkaline solutions, the Tafel slopes of the hydrogen evolution reaction were 180 mv and the rates of this reaction were independent of pH. The anodic Tafel slopes for copper dissolution in acidic solutions were 30 mv. The rate of anodic dissolution was increased by increasing the concentration of hydroxyl ions and the reaction order was about one-half. The pH dependence of the corrosion rate of copper in solutions of pH 0.35 to 5.8 was d log i_corr/d pH = −0.4.