What is the difference between hot-dip galvanizing after fabrication and continuous hot-dip galvanized sheet?
The process steps are similar but the production equipment is very different. After fabrication galvanizing is a more manual process where structural steel (fabricated plate, wide-flange beams, angles, channels, tube, pipe, fasteners) is suspended by wire, chain or hook from crane hoists and immersed in the cleaning solutions and zinc. Continuous sheet galvanizing involves uncoiling sheet, passing it through the cleaning steps and molten zinc bath at speeds up to 500 feet per minute, drying and recoiling. The uses of after-fabrication galvanized steel are usually exterior in nature because the zinc coating is relatively thick (3.0 – 6 mils, 75 – 150 microns, 1.7 to 3.6 oz/sq. ft.) and will protect steel from corrosion in most atmospheric conditions for 50 to 100 years. Galvanized sheet is suitable for interior applications because of the relatively thin coating (0.45 oz on each side), unless it is painted after galvanizing.
