THE EFFECT OF SPECIMEN SIZE, SHAPE, AND ORIENTATION ON DRY DEPOSITIONTO GALVANIZED STEEL SURFACES

Galvanized steel specimens varying in size, shape, orientation angle a nd previous exposure history (weathered specimens) were exposed at Res earch Triangle Park, NC, in the absence of natural precipitation. The soluble corrosion products were assumed to represent the effects of dr y deposition of airborne substances. The statistical analysis of their variability in relation to atmospheric conditions suggested that thes e substances included sulfur dioxide, nitric acid, hydrochloric acid, and calcium (presumably from coarse particles). The specimen character istic most influencing inferred dry deposition was previous exposure h istory. Deposition of gases depended on surface condition (wetness), w ind speed, temperature, and to a lesser extent, orientation angle. Dep osition of particles depended on orientation angle. Loss of soluble zi nc from specimens varied with specimen size to the -0.2 power, even th ough Reynolds numbers based on average wind speeds and specimen length were well below those classically expected to produce turbulent flow.