Powder Coating Specification: A Checklist for Engineers
The difference between a coating that performs and one that fails early is usually written before the first part is coated. A precise specification protects you in procurement, in production and in any warranty dispute. This checklist covers the fields every powder coating specification should include.
Buyer Decision Snapshot
A complete powder coating specification defines resin, color, gloss, film thickness, cure, pretreatment, test methods, certificates, packaging and acceptance limits. Without those fields, quotes and quality claims become ambiguous.
Key Takeaways
- Ten fields turn a spec into something measurable: substrate, pretreatment, system, colour, gloss, thickness, cure, tests, documents and acceptance criteria.
- State thickness as a minimum or range plus the measurement method and locations.
- A colour code without a gloss level is not a complete specification.
- Acceptance should rest on batch COA values and a signed approved sample panel, not on a data sheet.
- Name the substrate and exposure: interior, exterior, coastal or chemical.
- Fix film thickness and cure as ranges, not vague words such as durable.
- Require COA, SDS and market certificates with the first order.
- Keep an approved panel as the visual and physical reference.
The Ten Fields Every Spec Needs
- Substrate material and surface condition, including castings or galvanized steel
- Pretreatment standard: blast grade, profile, and conversion coating
- Coating system: resin chemistry and any primer or topcoat layers
- Color reference: RAL, Pantone or approved physical sample
- Gloss level at the specified angle
- Dry film thickness as a minimum, with measurement method and locations
- Cure schedule matched to the part, not just the powder data sheet
- Performance tests: adhesion, impact, salt spray, UV and any special requirements
- Approvals and documentation: COA, RoHS, REACH, water-contact certificates
- Acceptance criteria: sample plan, tolerances and who approves
Writing Thickness and Test Clauses
Say what you will measure, where, and how many points. A typical clause reads: minimum 60 microns DFT on flat surfaces and edges, measured with a calibrated gauge per ISO 2360 or ASTM D7091, with three readings per part on a defined sample plan. Avoid average-only clauses, because they let thin edges pass.
Documentation That Survives Audits
- Batch COA with measured values, not just a statement of conformity
- Approved sample panel kept and signed for reference
- Incoming inspection records on your side
- Test reports for any guaranteed property, from an accredited lab where possible
Common Mistakes That Cost Money
- Specifying a color without a gloss level – the same RAL can look very different in matte and gloss
- Forgetting edge coverage on laser-cut and punched parts
- Using one spec for indoor and outdoor parts without separate clauses
- Accepting a data sheet as proof of performance without batch test records
Frequently Asked Questions
What should a powder coating specification include?
Include resin type, substrate and pretreatment, color and gloss, film thickness, cure window, exposure environment, test methods, certificates, packaging, and written acceptance limits. These fields make quotations and quality claims measurable.
Which film thickness should I specify?
Most general metal parts use about 60-120 micrometres, but the correct range depends on substrate, edge coverage, corrosion target and appearance. Specify a range and measurement method instead of a single unverifiable number.
Which certificates should be requested with the first order?
Request a batch COA, SDS, RoHS and REACH declarations where relevant, and any market-specific approval such as WRAS or ACS. Keep the approved sample and test panel with the specification.
How do I approve a powder coating supplier?
Send a complete specification, ask for a coated test panel and TDS, review the QC plan and COA format, then run the panel through your assembly or corrosion requirement before approving production.
Need More Information?
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