Editorial Feature

Galvanized Coatings - Surface Area Calculation Tables

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Hot-dip galvanizing is typically priced in dollars per ton; however, it is advantageous to also convert this to dollars per square meter to enable comparison with alternative coatings.

Furthermore, the conversion to square meters enables precise estimation of weight increase through the inclusion of the hot-dip galvanized coating. The surface area per ton can also be estimated using the following formula:

Surface Area per ton = 255/Section Area in mm

Mass per square meter of steel can be estimated using the following formula:

Mass per Square Meter (g/m2) = Section Thickness (mm) x 0.85

Section Thickness (mm) Surface Area/Tonne
(m2/tonne)
Mass/m2
kg/m2
Min Coating Thickness
(µm) per AS 1650*
Mass Increase (%)**
1 mm 255 7.85 45 µm (320 g/m2) 4.10
2 mm 127 15.70 55 µm (390 g/m2) 2.85
3 mm 85 23.55 55 µm (390 g/m2) 1.65
4 mm 64 31.40 70 µm (500 g/m2) 1.59
5 mm 51 39.25 70 µm (500 g/m2) 1.25
6 mm 42 47.10 70 µm (500 g/m2) 1.05
8 mm 32 62.80 85 µm (600 g/m2) 0.95
10 mm 25 78.50 85 µm (600 g/m2) 0.75
12 mm 21 94.20 85 µm (600 g/m2) 0.65
15 mm 17 117.75 85 µm (600 g/m2) 0.50
20 mm 13 157.00 85 µm (600 g/m2) 0.40
25 mm 10 196.25 85 µm (600 g/m2) 0.30

* Heavier steel sections and hot-rolled steel sections will create galvanized coatings that are significantly thicker than required by the AS 1650 Standard. The following formula can be used to convert coating thickness in microns to equivalent coating mass in grams per square meter (g/m2):

Coating Mass (g/m2) = Coating Thickness (µm) x 7.05

Coating Thickness (µm) = Coating Mass (g/m2) x 0.14

**Actual zinc pickup after galvanizing will rely on the average thickness of coating and section design.

Zinc entrapment, poor drainage, and enormous horizontal surfaces will lead to higher zinc pickup.

Note: The usage of actual zinc in hot-dip galvanizing is considerably higher when compared to physical zinc pickup. In hot-dip galvanizing, zinc usage is usually 5%–7% of the mass of steel dipped due to the consumption of zinc on jigs and in producing zinc dross and zinc ash in the galvanizing process.

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