How is G90 galvanized steel different from F2329 (or A153) hot dip galvanized steel?
Both are produced via the hot dip process, but with slightly different processing steps. G90 is a coating grade within the steel sheet specification ASTM A653, and is produced by uncoiling steel coils and running it at high speed through the pickling process and molten zinc before it passes through an air curtain, which creates the smooth finish to the specified thickness. For G90 this thickness is 0.90 oz/sq ft, which is the total for both sides of the sheet, or 0.45 oz/sq ft per side. Compare that to hot dip galvanizing per ASTM F2329, where the minimum required thickness is 1.0 oz/sq ft, but that is measured on just one surface of the bolt, so it is more than twice the thickness required by G90. Because of the small amount of zinc applied to G90 sheet, it is primarily used for either interior applications, or in exterior applications where it will be painted, like auto body panels. Hot dip galvanizing per F2329, A153, or A123 is much thicker and intended to protect steel placed outside in harsh weather conditions.