ATMOSPHERIC CORROSION EFFECTS OF SO2 AND O-3 ON LABORATORY-EXPOSED COPPER

Copper samples were exposed for 10 days in synthetic laboratory air at 75% relative humidity. To explore the possible influence bf ozone on the atmospheric corrosion rate of copper, various combinations of the gaseous pollutants sulfur dioxide, nitrogen dioxide, and ozone were ad ded. Ozone promotes the oxidation of sulfur dioxide to sulfate more ef ficiently than nitrogen dioxide does. A synergism between sulfur dioxi de and ozone is suggested. This synergism includes both the oxidation of sulfur dioxide by ozone and the capability of ozone to form oxides, hydroxides, or other oxygen-containing reaction products in the prese nce of smaller amounts of sulfur dioxide. The synergistic effect possi bly can explain the unexpectedly high corrosion rates of copper found at rural sites within the UN ECE exposure program. The rural sites are characterized by low sulfur dioxide and nitrogen dioxide concentratio ns, and by high ozone concentrations.