Powder Coating Specifications: What to Put on a Coating Callout

Why the callout decides how fast you get a quote

When an RFQ says only “powder coat black,” the estimator has questions before a price can go out. Which black? What gloss? How thick? Which holes stay bare? Does it need a certificate? Each question is an email, and each guess becomes padding in the price.

Products Finishing gives the same advice: define performance requirements first, and give the shop drawings, dimensions and quantities in writing so it does not pad for unknowns. We paint and coat to the specification on your drawing or PO and quote to that spec, so the clearer it is, the faster and tighter the number.

For how each item affects price, see what drives the cost of a coating job.

1. Specification, type and class

• Name the spec and the revision if your contract fixes one. If it does not, say “current revision” so nobody has to guess.
• Include type, class, grade or composition. Many specs cover several products. MIL-DTL-5541 conversion coating, for example, has Type I (contains hexavalent chrome) and Type II (does not), and Class 1A (maximum corrosion protection) versus Class 3 (low electrical resistance). A spec number without its type and class is only half a callout.
• Send the internal spec with the drawing. “Finish per ES-1042” means nothing outside your building.

Specs that often appear on powder coating callouts include:

Liquid CARC and aerospace callouts stack pretreatment, primer and topcoat specs, each with its own type. Our CARC painting guide shows how.

2. Color code, gloss and texture

Color is three separate requirements, and incomplete callouts often miss one.

Color. Use a code from a named system: a Cardinal product number, a RAL number, or an AMS-STD-595 (formerly FED-STD-595) number. We coat with Cardinal powders, so a Cardinal product number is the most direct callout. RAL and AMS-STD-595 numbers can be matched to a Cardinal stock or custom powder. Avoid “black,” “safety yellow” or “match sample” without a reference. If you need a match to a physical sample, send it.

Gloss. A RAL number sets color, not gloss. Give a numeric range in gloss units at 60° per ASTM D523, such as “60° gloss 80–90 GU,” rather than a word like “satin,” which means different things to different suppliers. Most powder data sheets, including Cardinal’s, report 60° gloss as a target with a tolerance. D523 recommends 20° for very high gloss (above 70 GU at 60°) and 85° for very flat finishes, so name the geometry if your spec uses one. AMS-STD-595 numbers carry sheen in the first digit (1 = gloss, 2 = semi-gloss, 3 = flat), so 17038 and 37038 are both black but very different finishes. See our AMS-STD-595 color guide for how the numbers read.

Texture. Smooth, fine texture, wrinkle, hammertone, metallic. It changes how a part matches its neighbors on an assembly, so write it down.

3. Chemistry and service environment

If your spec does not name a chemistry, tell us where the part lives. That decides the powder.

• Exterior or UV exposure: polyester, superdurable polyester or polyurethane. Cardinal’s color card notes that exterior powders start with T, C or P in its product numbering.
• Interior only: epoxy and hybrid powders are options, but Cardinal states that H and E powders are not suitable as exterior topcoats where color and gloss stability matter. Epoxy chalks in sunlight.
• Chemical, solvent or abrasion exposure: say what the part will see.
• Primer required: call out primer plus topcoat if your corrosion requirement needs a two-coat system.
• Export: if parts ship to the EU, say so. TGIC is classified as a mutagen in the EU and is on the REACH Candidate List of substances of very high concern, so TGIC-free (HAA) polyester is often specified for EU export. Cardinal asks customers to contact them about export.

4. Film thickness (DFT)

Film thickness is a common place for callouts to go wrong, because one number looks precise and is not.

• Give a range, minimum and maximum. Electrostatically sprayed powder runs roughly 1 to 10 mils, and DeFelsko notes that a factory spec of 2 to 5 mils with a ±1 mil tolerance is common. A single number (“3 mils”) leaves the acceptable band undefined.
• State the units. 1 mil is one thousandth of an inch, or 25.4 µm.
• Check the powder’s data sheet. Cardinal’s T009 TGIC polyester data sheet, for example, lists a test film build of 1.5 to 3.0 mils. A spec far outside the data sheet range is worth a second look.
• Say whether it is per coat or total on primer-plus-topcoat systems.
• Name the measurement method if you need one. ASTM D7091 covers nondestructive dry film thickness on metal, with magnetic gauges on steel and eddy-current gauges on aluminum. Say how many readings, and where, if your QC plan defines it.

Too thin risks poor coverage and corrosion. Too thick can cause poor adhesion, chipping, more outgassing on castings and galvanized steel, and parts that no longer fit, so mask fits and threads or design for the film build. Our guide to designing parts for powder coating covers tolerances on coated features.

5. Masking and plugging

Masking is hand labor and one of the biggest variables in a quote, so put it on the drawing.

• Identify each masked feature by datum, surface or view, with a hatch or a note: “Mask surface -B-,” “Plug all 1/4-20 tapped holes,” “No coating inside bore Ø.500.”
• Separate “must be bare” from “coating permitted.” If a face can take overspray but no full build, say so.
• Give a tolerance on the mask line if the edge position matters.
• Mark electrical ground or bonding points that need bare metal.
• Say whether threads may be chased after coating instead of masked.

Avoid “mask all holes” unless every hole really needs it. Our powder coating masking guide covers methods and how to draw them clearly.

6. Pretreatment and surface condition

Tell us what the spec requires and what condition parts arrive in.

• Required pretreatment or conversion coating, such as zinc phosphate on steel or a MIL-DTL-5541 chem film on aluminum. Put it on the RFQ so the quote shows how it will be handled.
• Blast standard, if one is required. SSPC/NACE standards define blast levels: SP 5 white metal, SP 10 near-white, SP 6 commercial, SP 7 brush-off. AMPP notes that a higher SP number does not mean better prep, so name the exact standard. We coordinate blasting through a partner as part of the coating job.
• Substrate: steel, aluminum, stainless, galvanized, cast. Castings and hot-dip galvanized often need an outgas pre-bake before coating.
• Arrival condition: oiled, laser oxide, weld spatter. A photo helps.

7. Quantity and release schedule

A piece price depends on how many parts run together.

• Quantity per release and estimated annual volume
• Whether the first lot is a first article or a pilot run
• Release frequency for repeat part numbers or blanket POs
• Mix of part numbers that share a color and could run together

8. Inspection, records and Certificate of Conformance

Say what proof you need with the parts before the quote, not at shipping.

• CoC wording. We provide a Certificate of Conformance on request. Under FAR 52.246-15, a CoC is a signed statement that the supplies conform to the contract requirements. Tell us what yours must reference: PO, part number and revision, spec, color, quantity, lot.
• Inspection plan. If your QC procedure calls for DFT readings, adhesion checks, color checks or sampling, attach it. On higher-volume programs we follow the customer’s QC procedure.
• First article. If the part goes into an AS9102 first article package, say what the finisher’s portion needs to include.
• Lab testing. We do not run certified lab testing such as salt spray in-house. If your spec requires lab reports for production lots, flag it on the RFQ so we can agree before quoting how those requirements will be met (for example, through your lab or a third-party lab).

9. Packaging and delivery

• Bulk, layered with interleaf, individually bagged or foam-separated
• Part-number labels, lot labels or counts per box
• Returnable containers or customer-supplied dunnage
• Ship, customer pickup, or pickup and delivery in Denver or Pueblo by arrangement

10. Due date

Give the date the parts must be at your dock, and say whether it is firm. Our standard lead time is about one week. Custom colors, pre-bakes, multi-coat systems and subcontracted blasting add time, and we say so on the quote.

A complete example callout

A complete powder coating note might look like this. The values are illustrative, not a recommendation for your part.

FINISH NOTES
1. POWDER COAT, TGIC POLYESTER, EXTERIOR SERVICE.
2. COLOR: RAL 7035 LIGHT GRAY. 60° GLOSS 80-90 GU PER ASTM D523. SMOOTH.
3. DFT: 2.0-3.0 MILS (51-76 µm) PER ASTM D7091, 5 READINGS PER PART.
4. PRETREAT: CLEAN AND PRETREAT PER ES-1042 REV C (ATTACHED).
5. MASK: SURFACE -A- AND ALL 10-32 TAPPED HOLES. NO COATING PERMITTED.
   GROUND POINT AT VIEW B TO REMAIN BARE METAL.
6. NO RUNS, SAGS, BARE SPOTS OR INCLUSIONS ON SURFACES MARKED "CLASS A."
7. CERTIFICATE OF CONFORMANCE REQUIRED, REFERENCING PO, P/N, REV AND LOT.

Copyable RFQ checklist

Paste this into your RFQ email. Fill in what you know and mark the rest “TBD.”

COATING RFQ CHECKLIST
[ ] Part number and drawing revision
[ ] Material / substrate (steel, aluminum, galvanized, cast, other)
[ ] Overall dimensions and part weight
[ ] Arrival condition (oiled, laser oxide, weld spatter, rust) + photo
[ ] Governing spec, revision, type and class
[ ] Powder or liquid; chemistry if specified
[ ] Service environment (interior / exterior / chemical / export to EU)
[ ] Color code and system (Cardinal, RAL, AMS-STD-595, sample)
[ ] Gloss range and geometry (60° unless your spec says otherwise) and texture
[ ] DFT min-max, units, per coat or total, measurement method
[ ] Primer required? (spec and DFT)
[ ] Pretreatment / conversion coating required
[ ] Blast standard if required (e.g., SSPC-SP 10)
[ ] Masking: features, bare vs. overspray OK, mask-line tolerance
[ ] Ground / bonding points to stay bare
[ ] Thread chasing allowed? Y / N
[ ] Cosmetic acceptance criteria (Class A surfaces)
[ ] Quantity per release and annual volume
[ ] First article or pilot lot? Release schedule
[ ] Inspection plan / QC procedure attached
[ ] CoC required? Required wording and references
[ ] Packaging, labeling and counts per box
[ ] Delivery method (ship, pickup, Denver / Pueblo delivery)
[ ] Need date at your dock; firm or flexible
[ ] Which governs if drawing and PO conflict

Common callout mistakes

• Color only. “Black powder coat” leaves gloss, texture, chemistry and thickness open.
• A color number standing in for a coating spec. A commercial coating matched to FS 34094 is a color match, not CARC. A CARC part needs the CARC spec named as well as the color.
• A single DFT value with no tolerance or unit.

When your package is ready, send the drawing and checklist through our quote request form. If something is still undecided, send what you have and mark the gaps.