Galvanized Steel Coating Designations
A coating designation only means something inside the standard that defines it. This guide takes EN 10346:2015, ASTM A653/A653M, JIS G 3302 and the electro-galvanized standards one at a time, states the unit and the measurement basis each of them uses, and then shows exactly what converts between them and what does not.
A coating designation across a coil section: the mass counted over both surfaces, and the thickness that mass works out to on each face.
What a Coating Designation Says
A coating designation is a code for how much zinc a coil carries, and it carries that meaning only inside the standard that defines it. Three ordering vocabularies are in daily use, and they are not one vocabulary in three spellings.
In ASTM A653/A653M the letter G marks a galvanize (zinc) coating and the numbers refer to the weight of zinc on the surface of the steel sheet in inch-pound units. In EN 10346:2015 the designation is the nominal coating mass in combination with the symbol for the coating type — Z, ZF, ZA, ZM, AZ or AS — with the mass expressed in grams per square metre, and that standard defines coating mass as the total mass of coating given for both surfaces. JIS runs on a third set of coating symbols again, numbered on its own scale.
Behind each number sits a measurement basis, and the basis is part of the specification rather than a footnote to it. ASTM designations for hot-dip coated sheet specify a minimum triple spot test value, which is the average of three edge-center-edge readings and a total-both-sides requirement, a minimum single spot test value, and a minimum single side requirement that is normally not less than 40% of the minimum single spot total-both-sides requirement. A code quoted without its standard, its unit and its basis is a number and not a requirement, which is why the sections below keep the systems apart instead of merging them into one chart.
How Coating Mass Is Measured
Coating mass is a measured quantity with a sampling rule attached, so an order has to name the rule as well as the figure. The sequence below is how a hot-dip coating figure is established and judged under the ASTM general requirements specification; the other systems ask the same questions in their own words.
Settle the surfaces first
Under ASTM A924/A924M, metallic-coated steel sheet is produced to various coating designations shown in the individual product specifications and, except for differentially coated sheet, the coating is always expressed as the total coating of both surfaces. Nothing else on the coating line of a certificate can be read until that is settled.
Take the triple spot average
The first value is a minimum triple spot test value: the average of three edge-center-edge readings, judged as a total-both-sides requirement. It is an average taken across the width, not a reading at a single point.
Then the single spot floor
A minimum single spot test value applies alongside it, again total both sides, together with a minimum single side requirement that is normally not less than 40% of the minimum single spot total-both-sides requirement. An average alone does not settle an argument about one thin reading.
Full-width sheet and slit sheet part company
The triple spot test only applies to the original, full-width as-coated sheet. Narrow sheet cut from full-width sheet is subject only to a minimum single spot test, total-both-sides requirement. Where material will be slit, write down which of the two acceptance rests on.
Where a floor per face is needed
The ASTM A653M single-side system is written differently again. 60G requires a minimum of 60 g/m² and a maximum of 110 g/m² of zinc on each surface for any single spot test, and the designation for each surface must be shown, for example 60G60G. A per-face requirement looks like that; it does not look like half of a total-both-sides number.
Name the test method
ASTM A924/A924M provides two methods for the coating weight test: the weigh-strip-weigh method and the X-ray fluorescence method. Where acceptance turns on the result rather than on the label, the method belongs in the order and on the certificate.
The general requirements travel with the product specification
Product furnished under ASTM A653/A653M shall conform to the applicable requirements of the latest issue of Specification A924/A924M unless otherwise provided, so the testing rules come from a document your order may never mention by name.
EN 10346: Z and ZF Designations
EN 10346:2015 writes the coating as a designation and the designation as a mass. The nominal coating mass is combined with the symbol for the coating type — Z, ZF, ZA, ZM, AZ or AS — and the mass is expressed in grams per square metre. In an order the number designating the nominal mass of coating means, for example, 275 = 275 g/m² including both surfaces, and the standard defines coating mass as the total mass of coating given for both surfaces. A figure written that way is never a figure per face.
Two coating types carry most EN orders. A hot-dip zinc coating (Z) is the application of a zinc coating by immersing the prepared strip in a molten bath of zinc in which the zinc content is at least 99%. A hot-dip zinc-iron alloy coating (ZF) is a zinc-iron coating produced by immersing the prepared strip in a molten bath of zinc and then annealing it, which produces an iron content of normally 8 % to 12 %.
The standard's own coating-mass table — Table 12, with the triple-spot and single-spot minima — is not in the public preview of EN 10346:2015, so it is not reproduced here. What follows instead is a mill restatement, shown as manufacturer data and labelled as such. ArcelorMittal's catalogue lists these EN 10346 zinc designations with a typical coating thickness per side:
| Designation (EN 10346) | Typical coating thickness per side |
|---|---|
| Z100 | 7.0 µm |
| Z140 | 10.0 µm |
| Z200 | 14.0 µm |
| Z225 | 16.0 µm |
| Z275 | 20.0 µm |
| Z350 | 25.0 µm |
| Z450 | 31.0 µm |
| Z600 | 42.0 µm |
Source: ArcelorMittal catalogue E20, manufacturer data. The same catalogue gives Z275 as a coating weight of 275 g/m² double sided with a typical coating thickness of 20.0 µm per side, and marks Z80 (80 g/m²) and Z725 (725 g/m²) as not included in the EN 10346 standard. SSAB lists Z450 as 32 µm rather than 31.0 µm and also lists Z180, which the ArcelorMittal table does not. That is what a typical value looks like when two mills publish one: guidance, useful for planning a caliper, and not a limit to reject a coil against.
The basis behind the EN numbers is stated by the same mills. SSAB says that for the EN 10346 coating designations it lists, the value is the minimum total coating mass of both surfaces, in triple spot test, and gives Z275 as a minimum total coating mass of 275 g/m² on both surfaces with a guidance value of 20 µm typical coating thickness per surface. Minimum, average of three readings, two faces together: that is the sentence an order needs to carry beside the code.
The mass is only one field of an EN designation. An EN 10346 order also states a letter for the coating finish (N or M), a letter for the surface quality (A, B or C) and a letter for the surface treatment (C, O, CO, P, PO or S). The standard's designation example is DX53D+Z100–M–B–O: steel DX53D with zinc coating, coating mass 100 g/m², minimized spangle (M), surface quality B, surface treatment oiled (O).
ASTM A653/A653M: G and Z Designations
ASTM A653/A653M is one standard with two unit systems inside it. It is applicable to orders in either inch-pound units (as A653) or SI units (as A653M); values in inch-pound and SI units are not necessarily equivalent, and each system shall be used independently of the other. That sentence is the whole discipline of this section: choose a system, order in it, and read the certificate in it.
The common inch-pound coating weight designations for galvanized sheet ordered as ASTM A653 or A1063 are G30, G40, G60, G90 and G115. In SI units, ordered as A653M or A1063M, the comparable coating mass designations are Z90, Z120, Z180, Z275 and Z350. The GalvInfo Center lists the whole ladder, from G01 [Z001], which carries no minimum, up to G360 [Z1100], with the listed value being the minimum coating weight [mass], total both sides of the sheet, triple-spot average. The full ladder belongs to the standard and is not reproduced here.
The SI steps asked for most often read like this, as listed by the GalvInfo Center:
| Designation, ordered as ASTM A653M | Minimum coating mass, total both sides, triple-spot average |
|---|---|
| Z90 | 90 g/m² |
| Z120 | 120 g/m² |
| Z180 | 180 g/m² |
| Z275 | 275 g/m² |
| Z350 | 350 g/m² |
In ASTM A653M, Z275 requires a minimum average triple spot test of 275 g/m² total-both-sides, tested per ASTM A924/A924M. The GalvInfo Center adds the second half of the requirement: a single spot test minimum of 235 g/m², total both sides, and normally not less than 40% on any one side.
One inch-pound step can be given in full from the same source, and it shows how the two test values sit together:
| G90, ordered as ASTM A653 | Value |
|---|---|
| Triple spot test average, minimum | 0.90 oz/ft², total both sides |
| Single spot test, minimum | 0.80 oz/ft², total both sides |
| Any one side | Normally not less than 40% of the single spot figure |
Zinc-iron alloy coatings have their own ladder inside the same standard. The common inch-pound galvannealed designations ordered as ASTM A653 are A25, A40 and A60; the SI coating mass designations ordered as A653M are ZF75, ZF120 and ZF180, where ZF120 requires a minimum average triple spot test of 120 g/m² total both sides.
There is also a per-side system, for orders that need a floor on each face rather than over the pair. 60G requires a minimum of 60 g/m² and a maximum of 110 g/m² of zinc on each surface for any single spot test, and the designation for each surface must be shown, for example 60G60G.
One caution belongs at the end of the section, and the American Galvanizers Association puts it bluntly: G30, G60 and G90 are not galvanizing specifications. They are coating thickness designations found in the continuous galvanizing specification ASTM A653 that refer to a dual-sided coating weight in oz/ft².
JIS G 3302: Z and F Designations
JIS G 3302 names its coating classes with its own symbols, and the number inside a symbol is not the coating mass in grams per square metre. Z27 is the class whose minimum coating weight in the triple-spot test on both sides is 275 g/m².
JFE Steel's catalogue restates the JIS G 3302 coating designations as follows. This is manufacturer data rather than the standard's own table, and the catalogue does not name the edition it restates:
| Coating designation | Minimum coating weight, triple-spot test, both sides |
|---|---|
| Z08 | 80 g/m² |
| Z10 | 100 g/m² |
| Z12 | 120 g/m² |
| Z18 | 180 g/m² |
| Z20 | 200 g/m² |
| Z22 | 220 g/m² |
| Z25 | 250 g/m² |
| Z27 | 275 g/m² |
| Z35 | 350 g/m² |
| Z45 | 450 g/m² |
| (Z60) | 600 g/m², subject to negotiation |
Source: JFE Steel catalogue B1E-004-11, manufacturer data. The same catalogue states that JIS H 0401 is applied to coating weight measurement for JIS G 3302 products, and marks Z60 as subject to negotiation.
Single-spot minima are harder to source. The figures on file come from JIS G 3302:1998, an edition that has since been superseded and is named here only so that the numbers can be placed in history. In that edition, coating mass symbol Z12 had an average coating mass in the triple-spot test of 120 g/m² and a minimum coating mass at a single spot of 102 g/m², total on both surfaces; Z18 had 180 and 153; Z27 had 275 and 234. Those are a record of how the table once read, not a current requirement, and this guide does not use them as one. Name the edition on your order and ask the mill to certify against that edition; the catalogue restatement above and the superseded text also differ in how they treat the heaviest and lightest classes, which is exactly the kind of drift an edition reference prevents.
Zinc-iron alloy coatings run on F symbols. Nippon Steel's catalogue lists F04, F06, F08, F10, F12 and (F18), with minimum coating masses on both sides by the triple spot method of 40, 60, 80, 100, 120 and 180 g/m², and by the one spot method of 34, 51, 68, 85, 102 and 153 g/m².
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Electro-Galvanized Designations Are Per Side
Electro-galvanized coatings are ordered on a different basis again, and the difference is not a detail: the figure is per side, not over both surfaces together.
EN 10152:2009 defines an electrolytic zinc coating (ZE) as the application of a zinc coating by electrolysis on a suitably prepared steel surface from an aqueous zinc salt solution by the use of an electric current. In an EN 10152 designation the numbers denote the nominal coating thickness on each surface: 50/50 means a nominal coating thickness of 5,0 µm on each side, written with the decimal comma the standard uses.
| System | What the number expresses | Example |
|---|---|---|
| EN 10152:2009 | Nominal coating thickness on each surface | 50/50, a nominal 5,0 µm on each side |
| ASTM A879/A879M | Minimum and maximum single spot test value on each surface, with the designation shown for each surface | 13Z13Z or 40G40G |
| JIS G 3313, as restated by JFE Steel | Minimum coating weight on one side | E16: 17 g/m² equal coating, 16 g/m² differential coating, and a reference standard coating weight of 20 g/m² on one side |
The JIS row is manufacturer data. The same JFE catalogue gives E24 as 25.5, 24 and 30 g/m² on those three counts, and reads a designation such as SECC letter by letter: SE is the JIS electrolytic zinc coated steel sheet standard, the next C means a cold rolled base metal (H = hot rolled), and the last letter is the classification, where C = commercial quality, D = drawing quality and E = deep drawing quality. ArcelorMittal's catalogue lists the two-sided electrogalvanised coating ZE 25/25 as 2.5/2.5 µm thickness per side and 18/18 g/m² weight per side, and ZE 50/50 as 5.0/5.0 µm and 36/36 g/m² per side.
The masses themselves sit well below the hot-dip steps. Electroplated zinc coated sheet applications involve either a coating mass of 50 to 80 g/m² per surface, used predominantly for automotive applications, or a coating mass of less than 25 g/m² for applications, often indoor, that do not require a high degree of corrosion protection. EN 10152:2009 notes that, as the mass of the zinc coating applied is relatively small, the material is not intended to withstand outside exposure without further chemical treatment and painting. Compared with a G90 hot-dip coating, even the heaviest coating masses of electrogalvanized product are considerably less than much of the hot-dip galvanized product in use today for exterior applications; conversely, production of hot-dip coatings as thin as the lightest electrogalvanized coatings is not practical.
At the same coating mass, read on the same basis, the two behave alike in corrosion terms: a coating mass of 100 g/m² will provide essentially the same amount of corrosion protection whether it is hot-dip galvanized or electrogalvanized. What cannot be done is to read a per-side electro-galvanized figure and a total-both-sides hot-dip figure as one number, or to convert between them as if the bases matched.
Coating Mass to Thickness
A coating mass converts to a thickness through the density of zinc, and that conversion is arithmetic rather than a matter of standards. What it cannot do is move a figure from one standard's basis onto another's.
| Conversion | Figure | Basis and source |
|---|---|---|
| Coating weight to coating mass | 1.00 oz/ft² = 305 g/m² | Unit conversion; GalvInfo Center |
| Coating mass to thickness, one layer | 1.00 oz/ft² = 0.00168 in = 305 g/m² = 0.0427 mm | Zinc density 7140 kg/m³; GalvInfo Center |
| What a G90 coating adds | About 1.6 mils (0.0016 inches, about 42 microns) to the total sheet thickness; about 0.0008 inches (21 microns) on each surface where the split is equal | ASTM A653 designation, total both sides; GalvInfo Center |
| G90 and G60 read as a thickness on one side | 0.90 oz/ft² listed with 0.77 mils; 0.60 oz/ft² listed with 0.51 mils | Coating weight total both sides, thickness one side; American Galvanizers Association |
| Z275 typical thickness per side | 20.0 µm in the ArcelorMittal catalogue; 20 µm as an SSAB guidance value | EN 10346 designation, coating weight double sided; manufacturer data |
| JIS coating thickness used with the nominal thickness | 0.026 mm for Z12, 0.034 mm for Z18, 0.054 mm for Z27 | JIS G 3302 as restated by JFE Steel, total for both sides |
Three of those rows answer different questions and should never be merged into one column. A mill's typical thickness per side is a guidance figure attached to a nominal mass. The American Galvanizers Association figure is a thickness on one side worked out from a coating weight over both. The JFE figure is a thickness the catalogue adds to the nominal sheet thickness for tolerance purposes, and the catalogue does not explain how it is derived.
Two arithmetic cautions follow from the same place. Halving a total-both-sides designation to reach a per-side thickness assumes the coating is split equally between the faces, which the designation itself does not require. And because metallic-coated sheet under ASTM A924/A924M is produced to thickness requirements expressed to 0.001 in. [0.01 mm] with the thickness taken as the total of the base steel and the coating, a thickness derived from a coating mass is not something to add to a quoted sheet thickness a second time.
G90 and Z275: What Converts and What Does Not
G90 and Z275 are the pair most often set side by side, so it is worth being exact about which part of that comparison is arithmetic.
G90 is an inch-pound coating designation of ASTM A653, with a nominal total coating-mass basis close to 275 g/m². Z275 is a metric coating designation used in specified standard systems: it appears in the SI designation system of ASTM A653M, where it requires a minimum average triple spot test of 275 g/m² total-both-sides tested per ASTM A924/A924M, and it appears in EN orders, where it is read against that standard's own definitions instead.
Inside ASTM the conversion is real. The GalvInfo Center gives G90 at 0.90 oz/ft² and Z275 at 275 g/m² as an example of converting the inch-pound designation of ASTM A653 into the SI designation of ASTM A653M, and both designations are minimum triple-spot averages, total both sides. In the same SI series the GalvInfo Center lists Z90 at 90, Z120 at 120, Z180 at 180, Z275 at 275 and Z350 at 350 g/m² minimum, total both sides, triple-spot average, and for Z275 a single spot test minimum of 235 g/m², total both sides, normally not less than 40% on any one side.
Carry a designation out of ASTM and into another standard system and it stops being arithmetic. Each system sets its own test basis, sampling rules, single-point and three-point requirements, and per-side requirements where they apply. The two designations are commonly compared, and a comparison of that kind is a cross-reference: it requires full specification review and stays subject to purchaser approval against the standard named on the order.
Two traps sit inside the letters themselves. In ASTM designations the letters reverse between products: for hot-dip galvanize, G before the numerals means inch-pound and Z means SI, total both sides in each case; for electrogalvanize, G after the numerals means SI units and Z means inch-pound units, single spot and single side in each case. And because the total-both-sides, triple-spot designators allow an uneven split of the coating, it is not possible to precisely convert them into single-spot, single-side designators, since the latter specify exact minimums per surface.
So an order names one standard, one designation from that standard, and the basis that designation is read on. A second code written beside it as a convenience is the one that eventually gets certified against the wrong table.
Coil Coating Is Not Batch Galvanizing
Two zinc systems share a name and share little else. Continuous coil coating, the route ASTM A653 specifies, puts zinc on strip long before your part exists. Batch hot-dip galvanizing coats finished articles after they are made. Designations, thickness classes and service-life data do not travel between the two.
The American Galvanizers Association states the first half of that plainly: G30, G60 and G90 are not galvanizing specifications; they are coating thickness designations found in the continuous galvanizing specification ASTM A653 that refer to a dual-sided coating weight in oz/ft².
The continuous line also sets its own limits on what a designation can ask for. As the strip emerges from the molten bath it drags out excess liquid metal, and a gas-wiping process leaves a controlled thickness of coating, usually expressed as weight (mass) of coating per unit area, on the strip surface. Hot-dip galvanized coatings can be applied at levels ranging from as low as 0.30 oz/ft² [90 g/m²] to greater than 2.00 oz/ft² [600 g/m²]. Below that window, the minimum coating thickness achievable by gas wiping becomes limiting at about 0.00025 inch [6.4 µm], and each production line has its own minimum and maximum coating capability as a function of sheet thickness. Above it, coatings thicker than about 2 mils (0.002 in.) [50.8 µm] often have coating sags.
Service-life charts cross the same border and should not. The American Galvanizers Association defines time to first maintenance as 5% rusting of the base steel surface and states that it is linear and directly related to the zinc coating thickness; the chart carrying that definition is drawn for batch hot-dip galvanized steel, so the principle travels and the numbers do not.
Choosing a Coating Level
Coating level is chosen against the environment and against the life the part has to reach. The points below are guidance from published sources, each with the condition it was published under; none of them is a statement about any particular coil.
- Indoor and relatively dryFor indoor applications where the environment is relatively dry, a G40 [Z120] or G60 [Z180] coating weight [mass] is usually sufficient.
- Outdoor and bareFor many outdoor applications of bare, unpainted galvanized sheet, the most common coating weight [mass] in use today is G90 [Z275].
- The zinc is spent, not permanentGalvanically protective coatings are eventually consumed by corrosion, which is why galvanized sheet has a definite life span: the time before corrosion of the steel begins. The amount of zinc applied is therefore important to the life of the product.
- Thickness buys time, roughly in proportionFor a galvanized coating the rate of corrosion is typically linear in most environments, so twice the coating thickness translates to twice the life. The life itself varies considerably between rural, marine and industrial atmospheres, so the proportion holds while the absolute figure does not travel.
- Read a service-life figure as a modelThe GalvInfo Center's service life chart indicates that a G90 coating will last 20 years before 5% red rust in an average suburban locale. That chart is based on calculated, modelled corrosion rates rather than on measured zinc consumption, so it is a planning figure and not a warranty.
- And read a maintenance chart for what it coversTime to first maintenance is defined by the American Galvanizers Association as 5% rusting of the base steel surface, and it is linear and directly related to the zinc coating thickness. The chart that carries the definition is drawn for batch hot-dip galvanized steel.
Writing the Coating on an Order
A quotation needs the grade, finish, thickness, width, length and quantity. On coated coil the coating is not one of those six fields but several, and each one has its own place in the designation. Written in the order below, the line cannot be read two ways.
- The standard, and its editionName the standard and the edition beside the designation. A coating code means what the edition defining it says it means, and the certificate has to be checked against the same document rather than against a chart found elsewhere.
- The steel name, then the coating symbolIn an EN 10346 order the steel is identified by the steel name or steel number followed by the symbol for the type of hot-dip coating, for example DX53D+Z (1.0951+Z), where +Z is the zinc coating.
- The mass, and the surfaces it coversIn EN 10346:2015 the nominal coating mass in combination with the symbol for the coating type (Z, ZF, ZA, ZM, AZ or AS) is the coating designation, and the mass is expressed in grams per square metre. The number designating the nominal mass of coating means, for example, 275 = 275 g/m² including both surfaces.
- Spangle is a separate letterIn an EN 10346:2015 order the coating finish is stated by a letter, N or M, separately from the number for the coating mass; in the standard's ordering example M stands for minimized spangle. A heavier mass does not choose the appearance for you, and a coating code is not the place to ask for one.
- Surface quality is a third letterAn EN 10346 order states a letter for the surface quality: A, B or C. SSAB describes surface quality B, the improved surface, as obtained by skin passing and having a matte appearance, and surface quality A, the normal surface, as having a shiny appearance.
- Surface treatment is a fourthAn EN 10346 order states a letter for the surface treatment: C, O, CO, P, PO or S. SSAB describes the options as chemical passivation (C), oiling (O), chemical passivation and oiling (CO) and unprotected (U), and notes that the temporary corrosion protection provided by oil is especially dependent on storage time, so long storage times should be avoided with oiled products. Steel sheet manufacturers use the terms passivation treatment and chemical treatment to mean one and the same thing, so the order has to state whether chemical treatment is required or not.
- Alloy coatings look different by natureISO 3575:2025 notes that zinc-iron alloy-coated steel sheet, designated ZF, is not spangled, is normally dull in appearance and, for some applications, can be suitable for immediate painting without further treatment, except normal cleaning. Appearance wording written for a zinc coating does not transfer to it.
- On a JIS order, name the measurement methodJFE Steel states that JIS H 0401 is applied to coating weight measurement for JIS G 3302 products, and that Z60 is subject to negotiation. Where acceptance turns on the coating result, the method belongs in the order as well as on the certificate.
- The whole string, read onceThe EN designation example is DX53D+Z100–M–B–O: steel DX53D with zinc coating, coating mass 100 g/m², minimized spangle (M), surface quality B, surface treatment oiled (O). Five decisions, one line, nothing left to a default.
Frequently Asked Questions
It depends which standard the order names, and the quantity behind it is the same in both. In EN 10346:2015 the coating designation is the nominal coating mass in combination with the symbol for the coating type, expressed in grams per square metre, and the number designating the nominal mass means, for example, 275 = 275 g/m² including both surfaces; the same standard defines coating mass as the total mass of coating given for both surfaces. SSAB, restating that standard, says the value it lists is the minimum total coating mass of both surfaces in triple spot test, and gives Z275 as 275 g/m² with a guidance value of 20 µm typical coating thickness per surface. In the SI designation system of ASTM A653M, Z275 requires a minimum average triple spot test of 275 g/m² total-both-sides, tested per ASTM A924/A924M. Name the standard on the order so the figure is checked against the right table.
They are not one order specification. G90 is an inch-pound coating designation of ASTM A653, with a nominal total coating-mass basis close to 275 g/m²; Z275 is a metric coating designation used in specified standard systems. Inside ASTM the conversion is genuine: the GalvInfo Center gives G90 at 0.90 oz/ft² and Z275 at 275 g/m² as an example of converting the inch-pound designation of ASTM A653 into the SI designation of ASTM A653M, and both are minimum triple-spot averages, total both sides. ASTM itself states that values in inch-pound and SI units are not necessarily equivalent and that each system shall be used independently of the other. Across standard systems the pair is commonly compared, and that comparison is a cross-reference: it requires full specification review and stays subject to purchaser approval.
Through the density of zinc. The unit conversion is 1.00 oz/ft² = 305 g/m². For galvanized and galvannealed sheet the relationship between coating mass and thickness, based on a zinc density of 7140 kg/m³, is 1.00 oz/ft² = 0.00168 in = 305 g/m² = 0.0427 mm, taken as one layer. A G90 coating contributes about 1.6 mils (0.0016 inches, or about 42 microns) to the total thickness of the coated sheet; equally applied to both sides, that is about 0.0008 inches (21 microns) of zinc on each surface. The per-side figure holds only where the coating is split equally, which a total-both-sides designation does not itself require.
The single spot test, on a narrower basis than the mother coil. The triple spot test only applies to the original, full-width as-coated sheet, and narrow sheet cut from full-width sheet is subject only to a minimum single spot test, total-both-sides requirement. Under ASTM A924/A924M the coating is in any case always expressed as the total coating of both surfaces, except for differentially coated sheet, so the surfaces do not change when the width does. Decide at the inquiry stage which stage the acceptance figure belongs to, because that decides what the certificate has to report.
Sources
- GalvInfoNote 1.1: Understanding Coating Weight Designations for Zinc-Based Coatings on Steel Sheet (Rev 4.0, Dec 2020)
- GalvInfoNote 2.5: Control of Coating Weight [Mass] for Continuous Hot-Dip Galvanized Sheet Products (Rev 1.2, Dec 2017)
- GalvInfoNote 1.6: Selecting Coating Thickness (Weight or Mass) for Galvanized Steel Sheet Products (Rev 1.2, Dec 2017)
- GalvInfoNote 2.1: The Continuous Hot-Dip Coating Process for Steel Sheet Products (Rev 1.2, Dec 2017)
- GalvInfoNote 2.2: The Continuous Electroplating Process for Steel Sheet Products (Rev 1.2, Aug 2017)
- EN 10346:2015 Continuously hot-dip coated steel flat products for cold forming – Technical delivery conditions (public sample: foreword, scope, terms, classification, ordering information)
- EN 10152:2009 Electrolytically zinc coated cold rolled steel flat products for cold forming – Technical delivery conditions (public sample)
- ISO 3575:2025 Continuous hot-dip zinc-coated and zinc-iron alloy-coated carbon steel sheet of commercial and drawing qualities (public sample)
- ASTM A653/A653M-23 Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process (abstract and scope page)
- ASTM A924/A924M-22a Standard Specification for General Requirements for Steel Sheet, Metallic-Coated by the Hot-Dip Process (abstract and scope page)
- Industry catalogue E20 – Hot dip galvanised steels
- Industry catalogue E10 – Electrogalvanised steels
- Metal coated formable steels, EN10346:2015 – DX51D, DX52D, DX53D, DX54D, DX56D, DX57D
- Hot Dip Galvanized Steel Sheet catalog (Cat. No. B1E-004-11)
- Electrogalvanized Steel Sheet catalog (Cat. No. B1E-003)
- DURGRIP™ hot-dip galvannealed steel sheets catalog (U019en)
- JIS G 3302:1998 Hot-dip zinc-coated steel sheets and coils (superseded edition, OCR text)
- Time to First Maintenance
- Continuous Sheet Galvanizing ASTM A653 (G60, G90) vs. Batch Hot-dip Galvanizing ASTM A123 (2010)
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