1995 Volume 44 Issue 4 Pages 240-246
Copper corrosion in a simulated acid rain has been investigated by the electrochemical impedance analysis, the galvanostatic catholic-polarization, FT-IR and ICP-AES. Effects of pH and the Cl- concentration on the rate and the mechanism of the corrosion were studied adding H2SO4 (or NaOH) and NaCl to the simulated acid rain respectively. The corrosion rate increased with decreasing pH, and with increasing Cl- concentration. Warburg impedance resulting from a diffusion process for dissolved oxygen was observed at pH below about 3. The rate determining step of corrosion was found to be a film formation/dissolution process at pH≥3.5, and to be a diffusion process for dissolved oxygen at pH≤2.9. The film thickness increased with Cl- addition to the simulated acid rain, but the film formed at the Cl- concentration of 1000mg·dm-3 was thinner than that of 100mg·dm-3. This decrease in the film thickness at the Cl- concentration of 1000mg·dm-3 may result from the formation of CuCl whose solubility is much greater than that of Cu2O which is one of the major components of the film at low Cl- concentrations. The corrosion rate is thought to be controlled by CuCl2- diffusion when the Cl- concentration is high.