SOME ASPECTS OF THE ATMOSPHERIC CORROSION OF COPPER IN THE PRESENCE OF SODIUM-CHLORIDE

The effect of NaCl in combination with O-3 and SO2 on the atmospheric corrosion of copper was investigated. Corrosion products formed after 4 weeks exposure were characterized qualitatively by X-ray diffraction and quantitatively by gravimetry and ion chromatography of leaching s olutions. Studies of SO2 deposition and O-3 consumption were preformed using on-line gas analysis. Large amounts of cuprite (Cu2O) formed in all environments at 70 and 90% relative humidity. The corrosive effec t of salt was strong in pure humid air and in air containing O-3 or SO 2. Corrosion rate was correlated to the amount of chloride applied to the surface and to humidity. In an atmosphere containing a combination of SO2 and O-3 at 90% relative humidity, corrosion was rapid in the a bsence of NaCl. In this case, small additions of NaCl [Cu-2(OH)(3)Cl], and malachite [Cu-2(OH)(2)CO3] were identified. In the presence of SO 2, brochantite [Cu-4(OH)(6)SO4], soluble sulfate, and an unknown phase occurred, while no tenorite or malachite was formed. The combination of SO2 and O-3 resulted in the formation of antlerite [Cu-3(OH)(4)SO4] and Cu-2.5(OH)(3)SO4 . 2H(2)O as well.