Concrete filled grid panels, and Exodermic™ decks should be hot dip galvanized for maximum corrosion protection. When galvanized in accordance with ASTM A123, the grid should be protected for many decades before corrosion becomes noticeable. See https://galvanizeit.org for more info.
Panel size should be limited to ensure pieces can be coated with a single dip in the kettle. Double dipping will result in panel damage and must be avoided. Typical max panels size should be limited to about 45' x 8'. Panels as wide as 9-6" can be dipped but will incur extra freight costs due to shipping permits.
Open grid panels can be manufactured as uncoated weathering steel, hot-dip galvanized, or painted to match the remainder of the structure. Galvanizing offers superior corrosion protection and is less expensive than painting. Galvanization is not recommended for diagonal grids with a length exceeding 25’ due to the sweep induced and the difficulty straightening these panels. Mill finish weathering steel is the lowest cost option for open grids but weathering steel is not appropriate in all conditions. Consult with BGFMA and/or visit https://www.steelconstruction.info/Weathering_steel for more information.