Corrosion of Copper in Deaerated and Oxygenated 0.1M H2SO4 Solutions under Controlled Conditions of Mass Transfer

Abstract

The corrosion behavior of copper in deaerated and oxygenated 0.1 H2SO4 solutions has been investigated using the rotating cylinder electrode under turbulent flow conditions. Potentiostatic polarization measurements were carried out at different bulk temperatures of 283, 288, 293 and 298 K and various speeds of rotation viz 100, 200, 300 and 400 r.p.m. The anodic dissolution of copper and the hydrogen evolution reaction, in deaerated and oxygenated solutions, are activation controlled processes dependent on the temperature of the solution. The anodic dissolution of copper is not mass transfer controlled. The results are consistent with a mechanism which suggests that oxidation of copper takes place in two steps of one electron each. The second step, i.e., cuprous ion (Cu+) oxidation, is the rate controlling. Moreover, the mechanism of hydrogen evolution reaction is a proton discharge upon the metal surface. The charge transfer of the oxygen reduction reaction is a 2e process in the range of bulk temperatures employed, i.e., the oxygen reduction is controlled by 2e process. Furthermore, the limiting current density value of the oxygen reduction reaction increases as the velocity of the fluid increases. The results, at a constant bulk temperature are consistent with Eisenberg et al theory for mass transfer to a rotating cylinder electrode surface.