Polyester powder coatings
Thermoset polyester coating families, exterior qualifications, surface preparation and cure controls for specifying a complete coating system.
Tags: consumables, coatings, polyester, powder-coating
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AkzoNobel's Interpon D2525 Matt lists an object-temperature window of 200°C for 10–20 minutes. Its test panels used 10 minutes at 200°C, 60–80 µm film and approved chrome-free pretreatment on 0.5–0.8 mm Al Mg1. The reported at least 90% gloss retention after 1,000 hours uses ISO 16474-2 xenon-arc exposure. Keep the specimen and exposure method with the result. Interpon D2525 Matt TDS, pp. 1–3
What the name identifies
Thermoset polyester powder forms a film and crosslinks resin with a hardener. Specify the selected product and separately verify exterior, corrosion and cure requirements. TIGER, powder coating resins
Specify the supplier series, product code, color, gloss or texture, preparation, primer, film, cure and acceptance tests.
Curing families and exterior use
The hardener matters as much as the word polyester:
| Family | Distinction relevant to selection |
|---|---|
| Carboxyl-functional polyester with TGIC | Uses triglycidyl isocyanurate as the crosslinker. |
| Carboxyl-functional polyester with HAA | Uses hydroxyalkylamide chemistry; a common TGIC-free route. |
| Epoxy/polyester hybrid | Polyester reacts with epoxy resin. Do not assume the exterior performance of a dedicated weathering-grade polyester. |
| Hydroxyl-functional polyester with isocyanate chemistry | Produces a polyurethane powder coating system; distinguish its product requirements from TGIC/HAA polyester grades. |
These are formulation families, rather than interchangeable powders. TIGER also lists glycidyl-esters as polyester crosslinkers, so “TGIC-free” alone does not completely describe every possible formulation. TIGER, resin chemistry
TIGER’s own TGIC-free changeover guidance identifies HAA as the replacement hardener and requires equipment cleaning, attention to the revised cure window and avoidance of mixing TGIC with TGIC-free powder. Its Series 138 and 149 illustrate another distinction: HAA chemistry is offered in both superdurable and standard polyester grades, with different stated AAMA compliance levels. Crosslinker choice therefore does not establish a durability class. Treat a chemistry change as a process change even when color and gloss remain nominally the same. TIGER, TGIC-free formulations and changeover
Durability classes, approvals and weathering evidence
Separate three questions: what performance class is required, which coating system has an approval, and which applicator is qualified to produce the finished work. QUALICOAT’s 26th-edition introduction, valid from 1 January 2026, distinguishes coating-system P-number approvals, pretreatment approvals and licences tied to inspected production sites. Its overall specifications cover equipment, materials and finished products, rather than powder alone. QUALICOAT 2026 introduction, terminology, specifications overview
Check the current approval record for the supplied system and its scope, including finish and color coverage. QUALICOAT publishes both currently approved and cancelled systems; a historical brochure or a generic “architectural polyester” description is insufficient procurement evidence. QUALICOAT approval register
Weathering evidence must retain its test method and endpoint. QUALICOAT identifies xenon-arc accelerated weathering, natural Florida exposure, gloss measurement and color measurement as distinct evaluations. Gloss retention, color change and chalking describe different changes; none alone establishes corrosion resistance. Do not convert chamber hours or Florida exposure years into a building’s service life or warranty. Specify the applicable standard edition and acceptance criteria instead of treating “superdurable” as a complete test specification. QUALICOAT 2026 introduction, referenced test methods
Preparation and film control
Start with the substrate and contamination. Cleaning removes oil, soil and other residues; mechanical preparation can remove rust or old coating and establish a surface profile. A conversion treatment then serves a different function, supporting adhesion and corrosion resistance. Select the sequence with the pretreatment and coating suppliers for the actual metal, soils and exposure. A cleaner suitable for one alloy or contaminant is not automatically suitable for another. TIGER, pretreatment guide
Control concentration, time, temperature, rinsing and drying as part of that sequence. Cleanliness checks are process observations, not substitutes for finished-system corrosion testing. TIGER describes water-break, wipe and residue checks, while emphasizing the contribution of conversion coatings to the final coating system. TIGER, cleanliness and conversion treatment
Measure the cured film on representative surfaces, including difficult geometry. Increasing thickness is not a universal repair for poor appearance or protection. TIGER’s January 2022 troubleshooting guide associates appearance defects with excessive or uneven build, inadequate coverage, application conditions and cure differences. It also distinguishes contamination, pinholes and poor flow as separate fault investigations. Use the defect’s location and process history to narrow the cause before changing powder output or bake settings. TIGER troubleshooting guide, sections 3–5
Part temperature and a bounded product example
Use the part-temperature profile and the supplier’s full cure window. In a simple planning example, eight minutes of heat-up plus ten minutes of dwell gives eighteen minutes in the oven. PCI technical FAQ
Interpon D2525 Matt, EMEA TDS Ver28, 30 April 2026, illustrates how much context a product claim needs:
- TGIC-free polyester for architectural aluminium and galvanized steel; stated QUALICOAT Class 2 and AAMA 2604 performance, with listed color exclusions.
- Minimum application thickness 60 µm; laboratory results use 60–80 µm on 0.5–0.8 mm Al Mg1, with approved chrome-free pretreatment.
- Object-temperature windows: 180°C for 15–35 minutes, 190°C for 12–25 minutes, or 200°C for 10–20 minutes. Test panels were cured for ten minutes at 200°C.
- Reported accelerated weathering includes at least 90% gloss retention after 1,000 hours of ISO 16474-2 xenon-arc exposure. Its 1,000-hour acetic-acid salt-spray result has separate blistering and infiltration criteria.
These results belong to the described system and test conditions; they are not universal polyester properties. Interpon D2525 Matt TDS, pp. 1–3
For release, retain the approved product identity, preparation record, measured film and cure profile alongside the required test results. Resolve outdoor corrosion, postforming, repair and cleaning requirements with the supplier for the actual construction. Cosmetic weathering approval and a passing laboratory coupon do not by themselves qualify every joint, edge or production assembly.