Galvanized steel coil

01

Read the coating mass designation

GalvInfo, the International Zinc Association's galvanizing information centre, explains that ASTM A653 designations such as G90 give the minimum coating weight on both sides together: G90 means at least 0.90 oz/ft² as the triple-spot test average, and 1 oz/ft² = 305 g/m², so G90 corresponds to Z275, a minimum of 275 g/m² total of both sides. [1]

The same note lists the other limits for G90: a single-spot minimum of 0.80 oz/ft² for both sides and a single-side value "normally not less than" 0.32 oz/ft² on any one side. Coating weight is checked by weigh-strip-weigh, which also calibrates on-line X-ray gauges. Differential coatings are written per side, for example 90G60G. [1]

Editorial calculation: with zinc at 7,140 kg/m³, 275 g/m² ÷ 7.14 ≈ 38.5 µm of zinc in total, or about 19 µm per side if split equally; the 293 g/m² that GalvInfo's coating-factor table lists as the "Typical Actual Coating Mass" for Z275 gives about 41 µm, close to the roughly 42 µm it quotes for G90. [1] [2]

GalvInfo also notes that "for galvanized coatings in most applications and environments, the corrosion performance is an approximate linear function of coating weight": G90 is about 50% thicker than G60 and would be expected to last about 50% longer to 5% red rust. [1]

Give the supplier the standard and coating designation, test basis, steel grade, thickness and width with tolerances, surface treatment, spangle, oiling, coil ID, coil weight and end use.

02

Check grade, size and coil data

Huitong, a supplier listed here, offers galvanized coil from 0.12 to 3.00 mm (cold-rolled base), 600–1,500 mm wide, 508–610 mm coil ID, 3–8 t coil weight and 30–600 g/m² zinc coating, with big, regular, mini or zero spangle and oiled, passivated, chromated, skin-passed or anti-fingerprint surfaces. Its structural grades run from S220GD+Z to S550GD+Z; it lists S350GD+Z at 350 MPa minimum yield, 420 MPa minimum tensile and 14% minimum elongation. [3]

GalvInfo gives the theoretical mass of coated sheet as thickness × 7.85 kg/m² per mm minus a coating factor, which is 0.029 kg/m² for Z275. [2]

Editorial calculation: 0.5 mm Z275 sheet weighs about 0.5 × 7.85 − 0.029 ≈ 3.90 kg/m²; at 1,250 mm wide that is about 4.87 kg per metre, so a 5 t coil holds about 5,000 ÷ 4.87 ≈ 1,030 m of strip. [2] Check coil weight and ID against your decoiler.

03

Match the order to ASTM A653 or EN 10346 wording

ASTM's catalogue page for A653/A653M-23 says the specification covers "steel sheet, zinc-coated (galvanized) or zinc-iron alloy-coated (galvannealed) by the hot-dip process in coils and cut lengths", with coating weights [masses] or coating designations given in Table 1 and Table S2.1, and general requirements taken from the latest issue of A924/A924M. [4]

The unit rule matters on a quotation. ASTM states that values in inch-pound and SI units "are not necessarily equivalent", that each system shall be used independently, and that product is furnished to inch-pound units unless the order specifies the "M" designation. An order that reads G90 is an A653 inch-pound designation; an order that reads Z275 under A653M is the SI one. [4] GalvInfo gives the G90 to Z275 correspondence [1].

The EN 10346 abstract lists six coating families, Z, ZF, ZA, AZ, AS and ZM [5], while ASTM A653 covers zinc and zinc-iron only [4]. A supplier quoting "galvalume" or zinc-magnesium coil against A653 is quoting a coating that sits outside that specification's scope. Huitong offers base steel down to 0.12 mm [3], below the 0,20 mm figure in the EN 10346 abstract [5], so ask which standard covers the thinnest gauges on the offer.

Editorial calculation: the six EN 10346 coating families against the two in A653 leaves four (ZA, AZ, AS, ZM) that need a different ASTM or other specification on the order. [5] [4]

Values are from the ASTM store page and the Standard Norge catalogue page; the full texts were not reviewed.

04

Huitong's galvanized and colour-coated coil to JIS G3302 and ASTM A653

Huitong lists galvanized and colour-coated coil to standards including JIS G3302 and ASTM A653. [3]

05

Substrate, zinc layer, surface treatment, spangle and packing

Huitong's catalogue supplies the layer examples, from a DX51D or S350GD substrate to oiled, passivated or anti-fingerprint surfaces; the zinc layer's mass is set by the GalvInfo-explained designation. [3] [1]

06

Thickness, coating class, coil size and mechanical values for a galvanized coil order

Catalogue ranges in this table come from Huitong; the G90/Z275 equivalence and the 38.5 µm coating thickness come from GalvInfo. Coil outer diameter and winding tension are not stated in either source and need a supplier figure. [3] [1] [2]

07

Send the coating, steel and coil data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Coating: [standard; designation such as G90/Z275; per-side or differential; test basis]
Steel: [grade; thickness; width; tolerances]
Surface: [spangle; passivation or chromium-free; oil; anti-fingerprint]
Coil: [ID; maximum OD; weight range; packing]
Use: [roll forming, deep drawing, painting; environment]
Documents: [mill certificate; coating mass test; dimensional report]

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