PPGI vs PVDF vs SMP: How to Specify Colour Coated Steel Coil in Pakistan

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ahmed

July 25, 2026 On July 25, 2026

Three paint systems dominate colour coated coil quotations in this market — standard polyester (PE), silicone modified polyester (SMP) and PVDF. At spec grade all three are built to almost the same film thickness, roughly 25 microns on the top side. What you pay extra for is resin chemistry.

What actually decides how long a sheet lasts on a Pakistani roof is three other things: how much paint was really applied, the zinc coating mass underneath it, and who issues the guarantee and where it is enforceable. Resin name is the variable that gets argued about; it is not the variable that decides the outcome.

This page uses European and US mill datasheets as the yardstick, because those mills publish numbers you can check. Almost none of that coil lands in Karachi. The point of quoting it is to show what a given paint name is supposed to mean at spec grade, so you can hold a Chinese, Korean or local offer against it. The one Pakistani reference here is International Steels Limited (ISL), whose published product data is quoted with its date.

How thick is the paint on PPGI? PE, SMP and PVDF compared

The cleanest proof that the three systems are built alike comes from one coatings manufacturer quoting two of its own products on the same basis. Sherwin-Williams lists Fluropon (70% PVDF) at 0.2–0.3 mils primer, 0.7–0.8 mils topcoat, 0.9–1.1 mils total top side. Its WeatherXL SMP is listed at the identical three figures, and both sheets specify the same 0.5–0.7 mils on the back. Same house, same measurement method, same build. A seller describing PVDF as “thicker paint” is describing something the datasheets do not show.

ArcelorMittal works in microns and lands in the same place. Granite Standard polyester and Granite HD (high-durability polyester) are both 25 µm total, published as 5 µm primer plus 20 µm top coat. Granite PVDF 25 microns is published as 25 µm total with no composition row at all — the datasheet gives no primer/top-coat split for it. Isopan does publish a split for its own PVDF at 25 µm: 5 µ primer plus a 20 µ PVDF enamel.

System / product	Total top-side build	Primer	Top coat	Back side	Source
Polyester (PE) — ArcelorMittal Granite Standard	25 µm	5 µm	20 µm	5, 7, 10 or 12 µm backing coat	ArcelorMittal datasheets
High-durability polyester — Granite HD	25 µm	5 µm	20 µm	5, 7, 10 or 12 µm	ArcelorMittal datasheets
Granite HDS	35 µm	15 µm	20 µm	5, 7, 10 or 12 µm	ArcelorMittal datasheets
Granite HDX	55 µm	25 µm	30 µm	10 or 12 µm recommended (25 µm available)	ArcelorMittal datasheets
Granite PVDF 25 microns	25 µm	no composition published — total thickness only			ArcelorMittal datasheets
Granite PVDF 35 microns	35 µm	15 µm	20 µm	5, 7, 10 or 12 µm	ArcelorMittal datasheets
Granite PVDF 45 microns	40–45 µm	no composition published			ArcelorMittal datasheets
Granite PVDF 60 microns	55–80 µm	no composition published			ArcelorMittal datasheets
Standard polyester (PS) — Isopan	25 µm	5 µm	20 µm	5–7 µm, “back coat paint without guarantee”	Isopan / Manni guide
PVDF 25 µm — Isopan	25 µm	5 µm	20 µm PVDF	5–7 µm	Isopan / Manni guide
Thick resins PUR-PA — Isopan	50–55 µm	“more than the standard 5 µ”	not stated	not stated	Isopan / Manni guide
Plastisol PVC (P) — Isopan	100–200+ µm	not stated	not stated	not stated	Isopan / Manni guide
SMP — Sherwin-Williams WeatherXL	0.9–1.1 mils (22.9–27.9 µm)	0.2–0.3 mils (5.1–7.6 µm)	0.7–0.8 mils (17.8–20.3 µm)	back primer 0.3–0.4 + backer 0.2–0.3 mils = 0.5–0.7 mils (12.7–17.8 µm)	Sherwin-Williams PDS
PVDF 70% — Sherwin-Williams Fluropon	0.9–1.1 mils (22.9–27.9 µm)	0.2–0.3 mils (5.1–7.6 µm)	0.7–0.8 mils (17.8–20.3 µm)	primer & backer 0.5–0.7 mils (12.7–17.8 µm)	Sherwin-Williams PDS
Colour coated steel — International Steels Limited	20–60 µm including top coat, back coat and primer				ISL product page, July 2026

Conversions in that table use 1 mil = 25.4 µm.

Two things fall out of it. First, when a mill genuinely sells a thicker system, most of the extra build goes into the primer — Granite HDS is 35 µm as 15 µm primer plus the same 20 µm top coat. Only at 55 µm does the top coat move, to 30 µm. Isopan puts the logic plainly: raising thickness is itself a corrosion strategy, because a thicker paint layer is a bigger physical barrier against pollutants.

Second, and this is the line that matters locally: the last row is not measured on the same basis as the rest. ISL publishes its colour coated coating thickness as 20–60 microns including top coat, back coat and primer. A product at the bottom of that range is legitimately 20 µm across all three layers on both faces — well under the 25 µm top-side-only build the European sheets describe. So “25 micron paint” on an offer tells you nothing until you know which layers it counts and which side it is on.

Fix that in the paperwork rather than in the argument. Ask for top-coat dry film thickness (DFT) and back-coat DFT as separate line items on the mill test certificate, each stated per side, and make the numbers a condition of the order rather than a note in an email. On arrival, a DFT gauge on the coil at three points across the width is a five-minute check.

The back coat is where quoted specifications go quiet

Standard back coats in these ranges run from 5 to 25 µm, and Isopan’s guide labels its standard 5–7 µm back paint as “back coat paint without guarantee”. Sherwin-Williams specifies the same 0.5–0.7 mils on the reverse of both its SMP and its PVDF, so on those two products the back side is not a differentiator.

On a single-skin shed, where the underside is the ceiling and takes the condensation, the back coat is doing real work. Ask for it in microns, in writing, and ask whether it is guaranteed.

PVDF vs SMP vs polyester: what actually differs

Sunlight causes photo degradation of the binder, which shows up as colour change, gloss loss and eventually chalking. PVDF resists it because, as Isopan explains, its chemical structure has no organic functional group available to attack. ArcelorMittal classifies its PVDF products as thermoplastic paints and the rest of its Granite range as thermosetting — a real chemical difference, not a marketing one. Those datasheets do not name resin families beyond that, so nothing below calls a Granite product “polyester” unless ArcelorMittal does.

EN 10169 grades UV performance as an RUV class and corrosion as an RC class. The figures below are ArcelorMittal’s own reported QUV (UVA + water) 2,000-hour results and EN 13523-8 salt spray hours for each product, not the standard’s numeric definitions.

Product	Build	QUV 2,000 h	RUV	Salt spray (EN 13523-8)	RC	Guarantee	Metallic coating the figures refer to
Granite Standard (polyester)	25 µm	ΔE ≤ 5; GR ≥ 30%	RUV2	360 h	RC3	10 years	Z225 or Optigal ZM100
Granite HD	25 µm	ΔE ≤ 3; GR ≥ 60%	RUV3	360 h	RC3	10 years	Z225 or Optigal ZM100
Granite HDS	35 µm	ΔE ≤ 2; GR ≥ 80%	RUV4	500 h	RC4	20 years	Z225 or Optigal ZM120
Granite HDX	55 µm	ΔE ≤ 2; GR ≥ 80%	RUV4	700 h	RC5+ (colour cat. 1–4) / RC5 (cat. 5)	35 years	Z225
Granite PVDF 25 microns	25 µm	ΔE ≤ 2; GR ≥ 80%	RUV4	360 h	RC3	15 years	Z225
Granite PVDF 35 microns	35 µm	ΔE ≤ 2; GR ≥ 80%	RUV4	500 h	RC4	20 years	Z225
Granite PVDF 45 microns	40–45 µm	ΔE ≤ 2; GR ≥ 80%	RUV5	500 h	RC4	20 years	Z225
Granite PVDF 60 microns	55–80 µm	ΔE ≤ 2; GR ≥ 80%	RUV5	500 h	RC4	20 years	Z225

The product names on the last two rows are not the delivered thickness. Granite PVDF 45 is specified at 40 to 45 microns and Granite PVDF 60 at 55 to 80 microns. If a specification says “60 micron PVDF”, it has quoted a product name, not a tolerance.

The commercially awkward lines are Granite HDS and Granite HDX. HDS is a thermosetting, non-fluoropolymer system at 35 µm and it matches every PVDF grade on the QUV result — ΔE ≤ 2, gloss retention ≥ 80%. HDX, also thermosetting, carries RC5+ and a 35-year guarantee at 55 µm, while PVDF at 25 µm carries RC3 and 15 years. PVDF buys colour stability at low film build. Total film build and primer thickness buy corrosion life. They are not the same purchase.

Salt spray says the same thing. At equal build, PVDF did not improve creep: Granite Standard, Granite HD and Granite PVDF 25 all report 360 hours. The number only moves with total build — 500 hours across the 35 to 80 µm grades (HDS and PVDF 35/45/60), and 700 hours at 55 µm on Granite HDX and Granite HFX Cool.

The two European sources also disagree about PVDF at 25 µm: ArcelorMittal rates it RUV4 and RC3, Isopan rates the same nominal build RUV3 and RC4, and Isopan only reaches RUV4 at 35 µm. voestalpine explains why such disagreements are normal — UV resistance category “depends heavily on color”, and a stated RUV class “is achievable only for colors noted” in the mill’s own shade table.

SMP has no published RUV or RC class in any of the four European ranges examined here, because ArcelorMittal Granite, voestalpine colofer, Ruukki GreenCoat and Isopan’s EN 10169-2 range contain no silicone modified polyester product at all. Those ranges step from polyester to high-durability polyester to thick urethane or thick PVDF.

Where SMP and PVDF are measured against each other

Sherwin-Williams publishes both systems against the same test schedule, which makes it the one clean SMP-versus-PVDF comparison available.

Criterion	SMP (WeatherXL)	PVDF 70% (Fluropon)
Colour, ASTM D2244, 20 yr South Florida	≤ 5 ΔE at 90° vertical; ≤ 6 ΔE non-vertical	≤ 5 Hunter units (no angle qualifier stated)
Chalk, ASTM D4214, 20 yr	≥ 8 at 90°; ≥ 7 non-vertical	≥ 8 (no angle qualifier stated)
Film integrity, ASTM G7	25 years	25 years
Salt spray, ASTM B117 at 1,000 h and 3,000 h — creep from scribe on Galvalume or HDG	≤ 1/8 in (3 mm)	≤ 1/16 in (2 mm)
Specification compliance	AAMA 2604-17A	AAMA 621-02 + AAMA 2605-17A
Total top-side DFT	0.9–1.1 mils	0.9–1.1 mils

Read the first two rows carefully. The SMP sheet splits its pass mark by exposure angle and relaxes it off the vertical, and it states the test basis as “45 degree southern exposure for panel racking”. The PVDF sheet states a single figure with no angle qualifier. On the ASTM D4214 chalk scale, 10 means no chalking and 0 means heavy chalking, so a requirement of “not less than 8” means almost none.

Which UV class does a Pakistani site need?

voestalpine publishes a geographic selection rule for choosing among its own colofer products: locations north of the 37th parallel north warrant RUV3, and locations south of it warrant RUV4. It adds an altitude ladder — RUV3 up to 900 m, RUV4 up to 2,100 m.

Pakistan runs from under 24°N to just over 37°N, so every populated location is south of that line; only uninhabited high mountain territory in the far north sits above it. Applying voestalpine’s rule to Pakistan is an inference — it is guidance for selecting colofer, not a recommendation voestalpine has published for this country — but the inference is straightforward, and it puts standard polyester at RUV2 below the band everywhere here, with high-durability polyester at RUV3 still one class short.

Altitude compounds it rather than relieving it. The published ladder stops at 2,100 m, and several of the northern hill sites sit above that. For those projects the table gives no recommendation at all, which is a reason to ask the mill directly rather than assume RUV4 covers you.

Which zinc coating do you need — Z60, Z120 or Z275?

This is the point most quotations skip. ArcelorMittal states on every Granite datasheet that its published performance figures “refer specifically to” a stated metallic coating — Z225 or Optigal ZM100 for Granite Standard and HD, Z225 or ZM120 for HDS, Z225 for HDX and the PVDF grades, Z275 for HFX Cool, all as guaranteed minimums. Below that zinc, the RC class, the salt spray hours and the guarantee no longer apply.

voestalpine shows the effect starkly. colofer plus 50 and colofer plus 65 are each listed at corrosivity category C3 on ZM120 and C5 on Z275 under DIN 55634:2018 — the same paint, two substrates, two categories apart.

The pairing rules follow. Isopan supplies standard polyester with zinc up to 200 g/m², HD polyester with at least 200 g/m², PVDF 25 µm with 200 g/m² minimum, and PVDF 35 µm with at least 275 g/m². Ruukki states that all its colour coated thin sheet is hot dip galvanised Z275. Since the zinc is constant across its range, the only variable left in Ruukki’s corrosivity table is the resin — and for C4 and C5 it will issue “only project-specific warranties… under certain restrictions”. Ruukki also notes that unpainted hot dip galvanised thin sheet is recommended only up to category C2, which is worth knowing if you are comparing plain GP sheet against a coated option.

That is not a contradiction of the rule that paint and zinc move together. Ruukki holds zinc constant because it is already at Z275. The incoherent specification is upgrading the resin while the substrate stays at the bottom of the ladder. ISL’s published hot dip galvanised range runs Z60 to Z275 to ASTM A653 and JIS G3302, so the whole ladder exists here — you have to buy up it deliberately, and say so in the contract.

EN ISO 12944-2, reproduced in Ruukki’s selection guide, is the tool for deciding how far up. It defines each corrosivity category by first-year thickness loss.

Category	First-year zinc loss	First-year low-carbon steel loss	Typical exterior atmosphere
C1 very low	≤ 0.1 µm	≤ 1.3 µm	—
C2 low	> 0.1 to 0.7 µm	> 1.3 to 25 µm	Low pollution, mostly rural areas
C3 medium	> 0.7 to 2.1 µm	> 25 to 50 µm	Urban and industrial, moderate sulfur dioxide; coastal areas with low salinity
C4 high	> 2.1 to 4.2 µm	> 50 to 80 µm	Industrial areas and coastal areas with moderate salinity
C5 very high	> 4.2 to 8.4 µm	> 80 to 200 µm	Industrial areas with high humidity and aggressive atmosphere; coastal areas with high salinity
CX extreme	> 8.4 to 25 µm	> 200 to 700 µm	Offshore; extreme industrial

Set that against the zinc you are actually buying. A Z275 coating is about 19 µm of zinc per face — the arithmetic is in the next section. At C4 the standard’s first-year loss is 2.1 to 4.2 µm. Corrosion rates fall after the first year and paint changes the exposure completely, so this is a severity comparison rather than a service-life formula, but it is the arithmetic reason coating mass, not paint name, sets the corrosion life of the sheet.

voestalpine maps marine exposure by distance from the coast: high salt content 0–3 km, medium 3–10 km, low 10–20 km, corresponding to RUV4/C4 within 3 km, RUV3/C3 within 10 km and RUV2/C2 within 20 km. Applying that band, a site inside 3 km of the water falls at C4 or above. No source cited here assigns a corrosivity category to any specific Pakistani location, so the category for your site is something to establish for that site rather than assume.

Ruukki is blunt about the top end: colour coated thin sheet “can be used in corrosivity categories C1–C3, and the best color coatings can also be used in category C4”, while C5 “should be evaluated on a case-by-case basis, with the understanding that long-term durability cannot be guaranteed”. It is not suitable for offshore CX at all.

BMT vs TCT: measure the base metal, not the sheet

A quoted thickness is either TCT (total coated thickness — steel plus zinc plus paint) or BMT (base metal thickness, the steel alone). The gap is not trivial, and a contract that does not say which one it means has not specified anything.

The coating arithmetic comes straight from GalvInfo’s published conversions. For zinc, 1.00 oz/ft² = 305 g/m² = 0.0427 mm total both sides. For a 55% Al-Zn coating, whose alloy density is 3,750 kg/m³, 1.00 oz/ft² = 305 g/m² = 0.0813 mm.

Designation	Coating mass, total both sides	Inch-pound	Total coating thickness	Approx. per face
Z60	60 g/m²	≈ 0.20 oz/ft²	0.0084 mm	≈ 4 µm
Z80	80 g/m²	≈ 0.26 oz/ft²	0.0112 mm	≈ 6 µm
Z120	120 g/m²	≈ 0.39 oz/ft²	0.0168 mm	≈ 8 µm
Z180	180 g/m²	≈ 0.59 oz/ft²	0.0252 mm	≈ 13 µm
Z275 (= G90)	275 g/m²	0.90 oz/ft²	0.0385 mm	≈ 19 µm
AZM150 (= AZ50)	150 g/m²	≈ 0.49 oz/ft²	0.0400 mm	≈ 20 µm
AZM165 (= AZ55)	165 g/m²	≈ 0.54 oz/ft²	0.0440 mm	≈ 22 µm
AZM180 (= AZ60)	180 g/m²	≈ 0.59 oz/ft²	0.0480 mm	≈ 24 µm

Thicknesses above are calculated from GalvInfo’s own conversion factors. GalvInfo’s text rounds the G90 case to “about 1.6 mils (0.0016 inches, or about 42 microns)… about 21 microns of zinc on each surface”; the exact figure from its conversion is 0.0385 mm, so treat 38–42 µm as the working range for a Z275 coating.

Then add the paint. A 25 µm top coat plus a 7 µm back coat is another 0.032 mm. So a sheet sold as “0.30 mm” TCT on Z80 with that paint system is 0.300 − 0.011 − 0.032 = 0.257 mm of actual steel. Specify BMT, and verify it the way GalvInfo describes: measure the coated thickness, strip the coating, measure the substrate. A micrometer on a stripped sample is the first physical check on arrival, before anyone reaches for a paint gauge.

Gauge numbers still circulate in the trade. The table below is the US Manufacturers’ Standard Gauge for galvanized sheet, which is a nominal coated thickness. The BMT columns are derived by subtracting the zinc from the conversion above; they are arithmetic, not a standard, and they ignore the paint.

Gauge (galvanized sheet)	Nominal thickness, inches	Nominal thickness, mm	BMT if coating is Z275	BMT if coating is Z80
20	0.0359	0.912 mm	0.873 mm	0.901 mm
22	0.0299	0.759 mm	0.720 mm	0.748 mm
24	0.0239	0.607 mm	0.568 mm	0.596 mm
26	0.0179	0.455 mm	0.416 mm	0.444 mm
28	0.0149	0.378 mm	0.339 mm	0.367 mm
29	0.0135	0.343 mm	0.304 mm	0.332 mm

Mills here quote in millimetres, and so should a contract. Ruukki’s published recommendations give a useful sanity check on what thickness an application needs: 0.50–0.70 mm for tile sheet, standing seam roofing and non-load-bearing trapezoidal profiles, 0.50–0.70 mm for cladding profiles and sandwich panels, and 0.70–1.50 mm for load-bearing trapezoidal roofing — in every case on Z275 plus colour coating. If the sheet is going to be roll formed into corrugated or trapezoidal profile, the profiling stretches the coating at every crown and valley, so formability class and coil age matter as much as the nominal thickness.

What a colour coated warranty actually promises

Start with the sentence that decides whether the rest of this section applies to you. ArcelorMittal states that its Granite guarantee “can be automatic in the case of buildings erected in Europe… or project-specific in other cases”. A Pakistani project is in the second category. Ruukki says the same in different words: country-specific warranties can be applied for, and buyers should contact the local sales office to confirm the warranty that exists in their country.

So the year figures below are not a document you hold. They describe what a mill that stands behind its product is prepared to put in writing, and they give you the limbs any warranty you are offered should be broken into.

Product	Non-perforation of sheet	Non-delamination of paint	Aesthetic appearance
Granite Standard (polyester)	≤ 10 years	≤ 10 years	≤ 5 years (ΔE ≤ 5; gloss ret. ≥ 30%)
Granite HD	≤ 10 years	≤ 10 years	≤ 5 years (ΔE ≤ 3; gloss ret. ≥ 50%)
Granite PVDF 25 microns	≤ 15 years	≤ 15 years	≤ 5 years (ΔE ≤ 3; gloss ret. ≥ 80%)
Granite HDX	≤ 35 years	≤ 35 years	≤ 5 years (ΔE ≤ 3; gloss ret. ≥ 80%)

The colour limb is capped at five years right across the range, including the 35-year product, and every limb is qualified by geographic location and paint colour category. A “35-year warranty” is a perforation warranty. Note also that the test threshold and the guarantee threshold are deliberately different numbers: Granite HD is tested at gloss retention ≥ 60% in the QUV table and guaranteed at ≥ 50%.

Ruukki splits the same idea by corrosivity category, and the coastal collapse is visible in its numbers. GreenCoat Pural BT matt for roofing carries a 50-year technical warranty and a 25-year aesthetic warranty at C2 and C3, falling to ≤ 20 years at C4 and ≤ 5 years at C5. Common use Polyester carries 30 years technical and 10 years aesthetic at C2–C3, with the C4 and C5 cells blank — those categories are project-specific only, under restrictions.

Two conditions travel with any such guarantee and are easy to breach. ArcelorMittal makes its cleaning constraints part of the conditions of the guarantee, and voestalpine requires that “any processing… must be carried out at room temperature and within six months of the agreed delivery date. Otherwise there can be no guaranty for relevant properties.” Coil that sits in a warehouse for months before roll forming is a live warranty issue — ask when the mill delivered it, not when your supplier bought it.

What actually protects a buyer here

Since the mill guarantee is project-specific at best, the protection has to be built into the transaction:

Third-party pre-shipment inspection by an established house — SGS, Bureau Veritas or Intertek — with the scope written to include coating mass and paint DFT, not only quantity and packing.
The mill test certificate as a documentary requirement of the payment terms rather than an afterthought, and named by type: EN 10204 distinguishes a type 2.2 test report from a type 3.1 inspection certificate issued by an inspection representative independent of the manufacturing department.
Independent coating-mass and DFT testing on arrival, before the material leaves the port area.
Substrate and coating mass stated on the certificate with the test basis — coating designations under ASTM A653/A653M are total-both-sides minimums verified by triple spot test to ASTM A924/A924M.

A related discipline applies to the guarantee document itself. Ask which legal entity issues it, what it covers limb by limb, what corrosivity category it assumes and which colours it applies to. A card that names no entity and no conditions is marketing collateral, not a warranty.

PPGI vs PPGL (Galvalume): which substrate for coastal Pakistan?

The shorthand that Galvalume is automatically the coastal answer needs correcting, and GalvInfo’s own comparison is the reason.

Exposure site	Environment	Ratio of average corrosion rates, 55% Al-Zn : galvanized
Kure Beach, NC — 25 m	Severe marine	3.8
Kure Beach, NC — 250 m	Moderate marine	8.2
Bethlehem, PA	Industrial	6.4
Saylorsburg, PA	Rural	18.7

GalvInfo defines the ratio as “the relative improvement of the 55% Al-Zn coating versus galvanize for coatings of approximately the same thickness (G90 [Z275] galvanize and AZ50 [AZM150] Galvalume)”, so a higher number is a bigger advantage for Al-Zn. The advantage is widest inland and narrowest at the surf line: right at the water it drops to under four times.

Galvalume is 55% aluminium, about 45% zinc, with roughly 1.5% silicon. GalvInfo is explicit that the silicon is there to control a brittle intermetallic layer and “is not added to enhance the corrosion performance”. The aluminium-rich dendrites act as a barrier while the zinc-rich interdendritic regions provide the galvanic protection that limits rust staining at sheared edges.

The exclusions matter for two common local end uses. GalvInfo records that some producers “neither recommend nor warrant” bare 55% Al-Zn alloy-coated sheet for animal confinement buildings, poultry among them, because waste decomposition by-products are extremely aggressive to the coating. Ruukki describes the same environment from the other side: on farms the conditions are very humid and the surfaces are exposed to ammonia, methane and hydrogen sulphide, so material selection needs special attention. For a poultry shed the interior specification — back coat, underside and fasteners — is doing more work than the top coat. Separately, bare 55% Al-Zn should not contact concrete, and GalvInfo extends that to dry, fully cured concrete such as the bottom track of an exterior steel-framed wall. Deep drawing is another weak point, where galvanised is generally preferred.

Then the coating-mass trap. Designations are total-both-sides, and 1.00 oz/ft² equals 305 g/m² for both coatings, so G90 equals Z275. But the two coatings have different densities, which is why AZM150 at 150 g/m² is approximately as thick as G90 at 275 g/m² — about 20 µm per face in both cases. The bare numbers 150 versus 275 mislead. GalvInfo is blunt on equivalence: because the coatings corrode by different mechanisms, “drawing a performance equivalency curve is not possible”, and there is no answer to the question of which Al-Zn coating equals G90.

On designations, ASTM A792/A792M lists AZ50 [AZM150], AZ55 [AZM165], AZ60 [AZM180] and AZ70 [AZM210], but GalvInfo names only the first three as the common outdoor building-sheet coatings and assigns AZ70 [AZM210] to corrugated steel pipe under A929/A929M. The local trade’s “AZ150” means the metric AZM150. One further asymmetry: galvanised coating life is approximately linear with coating weight, so G60 lasts roughly twice as long as G30, while 55% Al-Zn follows a flattening parabolic curve and does not behave that way. Our overview of PPGI, GI and Galvalume roofing sheets covers the substrate choice in more detail.

One commercial constraint before specifying PPGL: as set out below, Chinese Galvalume currently carries an anti-dumping duty that Chinese galvanised does not.

RAL is a colour standard, not a quality standard

RAL’s own position is unambiguous: “RAL does not set any limits beyond which a RAL Color is no longer a RAL Color”, and it “does not prescribe any color tolerances as they are subject to different trade-specific requirements”. RAL supplies reference samples through registers 840-HR and 841-GL and leaves tolerance setting to the parties, recommending that buyers agree signed pre-samples that form part of the contract.

The mills say the same in commercial terms. Every Granite datasheet carries the line that ArcelorMittal cannot guarantee visual consistency from one order item to another, that you should consider placing a single order for one building, and that standard samples serve only as a guide. Its user manual adds that “industry best practice is not to mix different orders for the same building”. RAL 9002 turns up as a standard back-coat colour — voestalpine’s colofer reverse backing coat is approximately RAL 9002 at 10–15 µm.

Which standards apply, and one that only half applies

AAMA 2603, 2604 and 2605 are cited routinely on PPGI offers. They are written for aluminium extrusions and panels — the AAMA comparison table is titled “Organic Coatings on Aluminum Extrusions and Panels”, and Sherwin-Williams describes AAMA 2604-17A on its SMP sheet as a specification for coatings “on Architectural Aluminum Extrusions and Panels” with no coil qualifier. AAMA 2605 is the partial exception: Sherwin-Williams cites it for Fluropon as the aluminium specification “(Coil Coating appendix)”, alongside AAMA 621-02, whose title is specific to “Coil Coated Architectural Hot Dipped Galvanized (HDG) and Zinc-Aluminum Coated Steel”. AAMA 621-02 is the steel-specific document, and it is listed as withdrawn and not replaced on the FGIA store.

Attribute (2013 editions, per the AAMA comparison table)	AAMA 2603	AAMA 2604	AAMA 2605
South Florida exposure	1 year	5 years	10 years
Colour change	“slight” change allowed	ΔE ≤ 5	ΔE ≤ 5
Chalk (ASTM D4214)	“slight” change allowed	rating not less than 8	not less than 8 (6 for white)
Gloss retention	“slight” change allowed	≥ 30%	≥ 50%
Minimum initial DFT	> 20 µm (0.8 mil)	> 30 µm (1.2 mil)	> 30 µm (1.2 mil)
Humidity resistance	1,500 h	3,000 h	4,000 h
Salt spray	1,500 h (B117)	3,000 h (B117)	2,000 h (G85 Annex A5)
Associated resin	baked enamel (acrylic/polyester)	50% fluoropolymer (SMPs such as WeatherXL also certify to it)	70% fluoropolymer (PVDF)

Those figures are from the 2013 editions shown in that comparison table, while the Sherwin-Williams sheets quoted above cite the 2017 “-17A” editions. Check which edition an offer is claiming.

For steel, the standards that do the work are EN 10169 (current edition EN 10169:2022) with the EN 13523 test series; EN 10346, ASTM A653/A924 and JIS G3302 for the hot dip galvanised substrate; ASTM A792/A792M for 55% Al-Zn; and ASTM A755 or JIS G3312 for the prepainted product. Older local specifications sometimes still name BS 2989 for galvanised flat products; EN 10346 is the current European reference and the one to cite in a new contract. Fire classification to EN 13501-1 is A1 for most of these systems, though voestalpine notes that for several colofer products A1 applies only in combination with its reverse backing coat.

On temperature, the metallic coating is not the limit — the paint is. GalvInfo states that 55% Al-Zn coated sheet withstands surface temperatures up to 750°F [400°C] without discoloration and up to 1200°F [650°C] without heavy oxidation and scaling. ArcelorMittal states a maximum continuous operating temperature of 100°C for the Granite systems, and voestalpine lists +80°C to +110°C across colofer. For ordinary roofing that ceiling is not the binding constraint. Where it bites is cladding on process buildings — furnace and boiler houses, re-rolling mills — and that is where the paint limit should be checked against the real surface temperature.

What ISL publishes, and what to confirm on any offer

International Steels Limited’s product page, as published in July 2026, lists polyester (PE), polyvinylidene difluoride (PVDF) and polyamide paint mediums for colour coated steel at 0.28–1.50 mm thickness, maximum width 1,219 mm, coating thickness 20–60 microns including top coat, back coat and primer, to ASTM A755, JIS G3312 and equivalent standards. Its hot dip galvanised (GP) range is 0.18–2.50 mm at Z60 to Z275, maximum width 1,250 mm, to ASTM A653, JIS G3302 and equivalent standards. No aluminium-zinc substrate is listed on that page.

Three things follow. SMP is not on that list, so an SMP quotation is not ISL material — establish which mill produced it and against what specification, because the warranty then rests entirely on the exporting mill’s certificate. Polyamide is on the list and is the least discussed of the three mediums; if it is offered, ask which standard the performance is declared against and what UV and corrosion classification the producer claims, because it does not map onto the EN 10169 RUV/RC framework used by the European ranges above.

Third, and most useful: the page lists both galvanized steel and cold rolled steel as substrates under colour coated steel, alongside aluminium and stainless. Colour coated cold rolled carries no metallic coating at all — the paint is the only protection — and it looks identical to PPGI on a pallet. This is a real product category across the market rather than one supplier’s quirk, and the regulator treats it as one: the National Tariff Commission’s current investigation was opened under the title “Color Coated Cold Rolled Steel Coils / Sheets” before being broadened. Always confirm the substrate and the zinc coating mass on the mill test certificate before buying colour coated coil.

The checks worth writing into an enquiry, in the order they save money:

Substrate: galvanised, aluminium-zinc, or cold rolled with no metallic coating.
Coating mass as a Z or AZM designation in g/m², stated total-both-sides, with the test basis.
BMT in millimetres, separately from any quoted TCT.
Top-coat and back-coat DFT in microns, per side, as separate lines.
Resin family by name, and the standard the performance is declared to.
Producing mill and works, not only the trading company on the invoice.
Who issues any guarantee, for which limbs, at which corrosivity category, and for which colours.

Anti-dumping duty on colour coated coil and Galvalume: where the cases stand

All of the following comes from the National Tariff Commission’s own published notices and case tables, checked on 25 July 2026. Duty positions change; confirm the position applicable on the day of clearance.

ADC 51 — colour coated, China and South Africa. The NTC made an affirmative final determination on 13 June 2018 and imposed definitive anti-dumping duties on colour coated coils/sheets above 0.23 mm thickness under PCT headings 7210.7020, 7210.7090, 7212.4010 and 7212.4090, on C&F value in ad valorem terms, for five years from 13 June 2018. The rates were 5.36%, 6.03% and 10.88% for the three Chinese producers selected for detailed examination, 7.32% for cooperating producers not selected, 10.88% for all other Chinese exporters, and 14.24% for all South African exporters. The NTC’s notice of impending expiry, dated 10 March 2023, recorded that the duties would terminate on 12 June 2023 unless a sunset review was initiated before that date. A sunset review was initiated on 12 June 2023, and the NTC’s review table records it as concluded on 12 November 2024, terminated.

ADC 73 — colour coated, China, current. The NTC initiated a fresh anti-dumping investigation on 25 April 2026, on an application from International Steels Limited received on 16 March 2026. The investigated product is “pre-painted, painted, color coated or organic coated flat CR steel in coils or not in coils whether or not with metallic coated substrate of zinc, aluminum-zinc or any other substrate coating”, of alloy or non-alloy steel, prime or non-prime, “either in the form of coils or plain sheets or profiled sheets including but not limited to trapezoidal, sinusoidal, corrugated or any other type of profiles”, under PCT headings 7210.7010, 7210.7020, 7210.7090, 7210.9010, 7210.9090, 7212.4010, 7212.4090 and 7225.9900. A corrigendum dated 14 May 2026 broadened the product description from “Color Coated Cold Rolled Steel Coils / Sheets” to “Color Coated Steel Coils / Sheets”. As at 25 July 2026 the Commission’s own case table shows the preliminary determination as in progress, with no preliminary or final determination published. The initiation notice states that a preliminary determination falls not earlier than 60 days and not later than 180 days from initiation.

ADC 37 — galvanised and Galvalume, China. This one already bites. The NTC had imposed definitive anti-dumping duties ranging from 6.09% to 40.47% on galvanized steel coils/sheets from China under PCT headings 7210.4110, 7210.4190, 7210.4990, 7212.3010, 7212.3090, 7225.9200 and 7226.9900, effective 8 February 2017 for five years and extended for a further five years from 8 February 2022 on conclusion of a sunset review. On an anti-circumvention final determination published 28 June 2025, the Commission extended the 40.47% “all other exporters/foreign producers” rate to imports of Galvalume steel coils/sheets from China — PCT headings 7210.6110, 7210.6190, 7210.6910 and 7210.6990 — with effect from that notification until 8 February 2027. Product originating in or imported from sources other than China is not subject to it.

The practical consequence for a substrate decision is direct: at present a Chinese aluminium-zinc substrate carries a duty exposure that a Chinese galvanised substrate of the same value does not, and painted product sits under a different set of headings again, with its own live investigation. Classification of a specific consignment is a matter for your clearing agent against the current tariff. Read the NTC PDFs directly rather than relying on trade press summaries, and see our note on the anti-dumping duty position on galvanised steel.

Storage, forming and the site details that undo a good coil

Service life is best expressed the way EN ISO 12944-1 does, tied to a corrosivity category: LOW under 7 years, MEDIUM 7–15, HIGH 15–25, VERY HIGH over 25. Ruukki’s guidance is to use colour coated steel only up to the category where HIGH durability can be guaranteed. None of the mill sources reviewed here publishes a Pakistan-specific service life figure, so treat any such number as an estimate and ask which corrosivity category, which coating mass and which paint system it rests on.

Cut edges need separate treatment in aggressive environments. ArcelorMittal’s user manual states that in harsh environments such as marine areas it may be necessary to implement edge protection, and that anti-corrosion varnish can significantly enhance protection of exposed edges, applied by brush or roller with a minimum coverage width of 2 cm on a degreased, dust-free surface. That is a site instruction rather than a coil specification, and it applies wherever a coil is sheared or roll formed into corrugated profiles, whoever does that work.

Cleaning is a guarantee condition in the European documents: contact time under 30 minutes, temperature below 30°C, rinsing pressure under 5 MPa and a neutral-pH product, with cleaning specifically required on parts not naturally washed by rainfall. Through a long dry season the parts not naturally washed by rainfall are effectively the whole roof, and the residue is dust rather than industrial fallout — worth remembering when someone quotes a European gloss-retention figure at you.

Two further failure modes are better designed out at order stage than diagnosed later. The first is condensation on the underside of an uninsulated single-skin roof, which is precisely why the back-coat specification above is not a detail. The second is fasteners: a stainless or properly coated self-drilling screw with a sound EPDM washer, driven to the right torque, costs a fraction of the coil and decides whether the roof streaks. Neither is a coil property, and neither is covered by a coil warranty.

FAQ

Which is better for a Pakistani roof, PPGI or PPGL (Galvalume)?

It depends on distance from the sea, and on duty. GalvInfo’s exposure data shows 55% Al-Zn outperforming galvanised by the widest margin inland (18.7 times at a rural site) and by the narrowest at the surf line (3.8 times at 25 m from the water). Against that, GalvInfo notes producers who neither recommend nor warrant bare Al-Zn for animal confinement buildings including poultry, and rules it out in contact with concrete. Commercially, the National Tariff Commission extended a 40.47% anti-dumping duty to Chinese Galvalume coils/sheets from 28 June 2025 until 8 February 2027, which Chinese galvanised does not carry. Decide the substrate on the site’s corrosivity category first, then check the duty position for the origin you are buying. Our comparison of PPGI, GI and Galvalume roofing sheets sets the two substrates side by side.

Is PVDF a thicker paint than polyester or SMP?

No. Sherwin-Williams lists its 70% PVDF and its SMP at the same 0.9–1.1 mils total top side and the same 0.5–0.7 mils on the back. ArcelorMittal publishes Granite Standard polyester at 25 µm as 5 µm primer plus 20 µm top coat, and Granite PVDF 25 microns at 25 µm total with no breakdown published at all. PVDF at standard build buys colour and gloss retention, not extra film. If you want extra film, buy extra film and specify it in microns.

What thickness should a roofing sheet be, and is that BMT or TCT?

Ruukki’s published recommendation is 0.50–0.70 mm for tile sheet, standing seam and non-load-bearing trapezoidal profiles, and 0.70–1.50 mm for load-bearing trapezoidal roofing, both on Z275. Whatever figure you agree, state whether it is BMT or TCT. A Z275 coating alone is about 0.039 mm and a 25/7 µm paint system another 0.032 mm, so a 0.30 mm TCT sheet on Z80 contains about 0.257 mm of steel. Gauge numbers are a nominal coated thickness, not a base metal thickness.

Is AZ150 Galvalume equivalent to Z275 galvanised?

No, and GalvInfo says the question has no answer — because the two coatings corrode by different mechanisms, a performance equivalency curve cannot be drawn. What is true is that AZM150 is about as thick as a G90 (Z275) coating, roughly 20 µm per face in both cases. The lower gram figure reflects the lower density of the aluminium-zinc alloy, not a thinner coating.

What does a “20-year warranty” on colour coated sheet actually cover?

Typically perforation and delamination for the headline number, and appearance for far less. In ArcelorMittal’s Granite range the aesthetic limb is capped at five years across every product, including the 35-year one, and all limbs depend on location and colour category. ArcelorMittal also states that its guarantee is automatic only for buildings erected in Europe and project-specific elsewhere, and Ruukki issues only project-specific warranties at C4 and C5. Ask for the warranty document and the issuing entity, not the number.

How long will a colour coated roof last in Karachi?

No mill source reviewed here publishes a Pakistan-specific figure, and a credible answer needs three inputs rather than one. Establish the corrosivity category for the site — voestalpine’s distance bands put anything within 3 km of the water at C4 or above — then read the durability range EN ISO 12944-1 assigns to it (HIGH is 15–25 years, MEDIUM 7–15), then confirm that the coating mass and paint system you are buying are rated for that category. Ruukki’s position is that colour coated steel should be used only up to the category where HIGH durability can be guaranteed, that C4 needs the best coatings, and that at C5 long-term durability cannot be guaranteed at all.

Sources

If you are specifying colour coated coil for a project and want the paint system, zinc coating mass, substrate and base metal thickness pinned down before you commit, contact Raw Easy Corp to discuss your enquiry.

Steel Guides

How to Read a Mill Test Certificate (MTC) for Steel Coil

Posted by

ahmed

July 25, 2026

A step-by-step guide to reading a mill test certificate for cold rolled, galvanized and galvalume coil — the EN 10204 document type, heat number traceability, grade chemistry, mechanical footnotes, coating mass notation, and why the mill name on the certificate decides your anti-dumping duty rate. Written for Pakistani importers and fabricators, with every figure attributed to the document it came from.

Steel Guides