How to use the galvanizing zinc weight calculator
Hot-dip galvanizing is quoted and ordered by the mass of zinc deposited per unit of surface area, not by the area alone. Enter the wetted surface area and the ASTM A123 coating grade, and this tool returns the coating mass in ounces per square foot, the total zinc weight in pounds, the average coating thickness, and the material cost if you supply a zinc price.
In ASTM A123 the grade number is simply the minimum average coating thickness in micrometers, and Table 1 assigns a grade based on material category and steel thickness. Thicker structural shapes and plate at or above 1/4 in typically call for Grade 100, while thin material drops to Grade 45 or 65. Zinc has a density of about 7.14 g/cm3, so 1 mil of coating equals roughly 0.6 oz per square foot.
When taking off the area, include pipe interiors, the back faces of angles and every other surface the bath will touch, because the kettle coats them all. Treat the result as an estimate for budgeting and confirm the specified grade, kettle size limits and any duplex coating requirements with the galvanizer before ordering.
Frequently asked questions
The grade number is the minimum average coating thickness in micrometers. Grade 75 means 75 micrometers, about 3.0 mils, which works out to roughly 1.7 oz of zinc per square foot.
Hot-dip galvanizing coats every exposed surface, so add up the entire wetted area including pipe interiors and the back faces of angles, not just the faces you can see.