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| Cleaning and Handling Proper preparation of the surface is necessary where rapid weathering and uniform appearance are desired. This is best accomplished by adequate sand or grit blast cleaning to remove all mill scale, the surface oxide which forms on hot-rolled steel as it cools in air. This preparation is especially recommended for the highly visible exterior or fascia members of bridges. Care should be taken in handling Weathering Steel in the field to avoid unsightly gouges and scrapes. The material should be kept as clean and free as possible from mud, grease, oil, paint, concrete or mortar splatter and other foreign substances to minimize costly on-the-job cleaning. Paint or crayon identification marks should be made in locations not visible on the finished structure. Otherwise, these marks must be removed from the visible surfaces during the final cleaning operation.
Storage in transit, in yards, or at jobsites should be minimized. When storage is unavoidable, uneven weathering can be minimized by positioning the material to allow open exposure and free drainage. Blocking, to avoid contact of exposed surfaces with the ground, is essential. Cover cloths may also be helpful in preventing water staining and the accumulation of dirt on surfaces to be exposed, thus minimizing problems of an initial, non-uniform weathered appearance. In general, the overall corrosion resistance and ultimate appearance of Weathering Steel is not affected by cleanliness. Mill scale and certain forms of minor soilage will ultimately weather off naturally on exposed surfaces and need not be a concern for interior members of low visibility. However, cleanliness and surface preparation are important where early, uniform appearance is aesthetically desirable.
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