TESTS FOR ATMOSPHERIC CORROSION OF METALS ALONG THE RUSSIAN-NORWEGIANBORDER .2.

The Norwegian Institute for Air Research and the Institute of Physical Chemistry, Russian Academy of Sciences, have completed the second sta ge of atmospheric corrosion tests carried out along the Norwegian-Russ ian border, where the sulfur dioxide emission levels are elevated. Dry sulfur deposition is shown to be the primary reason for enhanced atmo spheric corrosion of metals in this area. Dry chloride deposition, cau sed largely by marine aerosols, contributes to corrosion in Viksofjell and Karpdalen. In the atmosphere highly polluted by SO2 or by SO2 and Cl- ions, the corrosion rates for steel and zinc decrease by only 20- 50% after one-year exposure. Dose-response functions for one-year corr osion loss of carbon steel and Zn in the subarctic atmosphere strongly depend on the time of wetness. The determination of the SO2 corrosivi ty, i.e., the mean contribution from SO2 to the corrosion rate or the mean total corrosion rate over a period of wetness, is crucial for cor rosion monitoring and studying the trend effect. For the (SO2 + Cl-)-c ontaining atmosphere, the one-year corrosion rates for steel and Zn ar e higher than those in the atmosphere containing SO2 only.