G90

G90 is a coating designation used for hot-dip galvanized steel in North American practice. The “G” denotes galvanization, and the number indicates the coating weight. G90 specifies a total zinc coating of about 0.90 ounces per square foot of surface area, typically applied to both sides of the steel. This corresponds to roughly 275 grams of zinc per square meter. The coating weight helps predict corrosion resistance and service life in various environments.

Production and standards: The zinc coating is applied by hot-dip galvanizing, where the steel is immersed in molten zinc. The G-series designations are commonly defined within ASTM specifications for galvanized steel products, such as ASTM A653/A653M for sheet and strip. The G90 grade lies among heavier coatings that retailers and fabricators use for exterior and more exposed applications, alongside G60 and G40.

Coating thickness and durability: The zinc layer is approximately 1.9 micrometers thick on each side (about 3.8 micrometers total for two sides). Durability depends on climate; in mild outdoor environments, G90-coated steel can provide many years of protection, while exposure to coastal salt spray or industrial pollution reduces service life. Maintenance, paint over-coats, and coating quality also influence longevity.

Applications and use: G90-coated steel is widely used for exterior structural members, roofing and wall panels, fasteners, and other fabricated parts in construction and manufacturing. It sits between lighter coatings (e.g., G30, G40) and heavier ones for long-term corrosion resistance. Selection balances corrosion protection, weight, and cost, with environmental conditions often driving choice toward thicker coatings in harsher settings.