Specimens of iron, zinc, and aluminum were exposed to an air atmosphere containing
3000±500 normalppm CO2
, at
298±0.5K
and
97±2%
relative humidity for times up to 200 hr. To this atmosphere could be added separately or in combination
3.5 normalppm SO2
, 60 vpm isobutane, and smoke at 160 or 360 μg m−3. Corrosion was enhanced by
SO2
or smoke in all cases, and by isobutane plus
SO2
in the case of aluminum and zinc. In contrast, isobutane as a single pollutant slightly inhibited the corrosion of each metal, and the corrosivity of
SO2
in the case of iron. Possible mechanisms concerning the observed effects of smoke and isobutane are suggested. These include corrosion promotion by smoke via an enhancement of the microclimate activity of water and sulfur dioxide, and corrosion inhibition by isobutane via competitive reactions with water molecules.