Effect of Specimen Size, Shape, and Orientation on Dry Deposition to GalvanizedSteel Surfaces

摘要

An analysis is presented of the variability in chemical composition of solublecorrosion products on galvanized steel specimens exposed at Research Triangle Park, NC, in the absence of natural precipitation. The specimens varied in size, shape, orientation angle, and previous exposure history. The soluble corrosion products were assumed to represent the effects of dry deposition of airborne substances, which were deduced to include SO2, NOy (presumed HNO3), Cl(-) (presumably HCl), and Ca(+2) (presumably from coarse particles), based on statistical analysis of their variability in relation to atmospheric conditions. The most important specimen characteristic was previous exposure history. Deposition of gases was dependent upon surface conditions, wind speed, and temperature, and to a lesser extent orientation angle. Depositon of particles was dependent upon specimen surface orientation. Soluble zinc loss varied with Reynolds number to the -0.2 power even though Reynolds numbers based on average wind speeds were well below those classically expected to produce turbulent flow.