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Industrial painting: coverage and cost

Enter the area or structure weight, each coat’s dry film and volume solids, the application method and prices. Get gallons per coat, cost per square foot and whether the thickness meets the ISO 12944 corrosivity category.

Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.

Preliminary estimate
Surface
Environment and durability (ISO 12944)
Coating system

Example: zinc-rich epoxy, high-build epoxy and aliphatic polyurethane. Enter zero DFT to skip a coat. Take VS and price from the data sheet and the quote.

Application and costs
—Paint required (all coats)
—

Consumption per coat

Wet film, theoretical and practical coverage, volume and cost of each coat for the whole area.

System cost per ft²

Surface preparation, labor and paint for each coat.

Tap the chart to see the values.

Typical total DFT by category (ISO 12944-5)

Order of magnitude for epoxy and polyurethane systems at the chosen durability, compared with the system entered.

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Next step

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Weight and outside area of the parts →Galvanic corrosion risk at the joints →

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Method, assumptions and references

Equations used

Theoretical coverage: TC = 10 × VS (%) ÷ DFT (µm), in m²/L (= 1,604 × VS ÷ DFT in mils, ft²/gal)
Practical coverage: PC = 10 × VS ÷ (DFT + profile allowance) × (1 − losses); profile allowance on the first coat only
Wet film: WFT = DFT × (1 + thinning) ÷ VS; volume = area ÷ PC; thinner = volume × thinning
Area from weight = weight × specific area (ft²/ton); cost = Σ volume × price + labor × area × coats + preparation × area

Assumptions and limits

  • Typical losses by method: brush 10%, roller 15%, airless 25% and conventional spray 40%; open members and wind increase losses. Profile allowance of 0.4, 0.8 or 1.2 mils (dead volume) for fine, medium and coarse profiles.
  • Typical thicknesses by category are orders of magnitude for epoxy and polyurethane systems on steel blasted to Sa 2½ / SSPC-SP10 (ISO 12944-5 Annex C; CX per ISO 12944-9). Take the final system from the standard’s tables and the manufacturer’s specification.
  • Area per ton is an average by weight range. For the exact area, add up each member’s perimeter times length.

Standards and technical documents

  • ISO 12944-1, -2, -5 e -9: Paints and varnishes — Corrosion protection of steel structures by protective paint systems
  • ISO 8501-1: Preparation of steel substrates — Visual assessment of surface cleanliness
  • ISO 19840: Measurement of and acceptance criteria for the thickness of dry films on rough surfaces
  • SSPC-PA 2: Procedure for Determining Conformance to Dry Coating Thickness Requirements
  • ISO 3233-1: Determination of the percentage volume of non-volatile matter

U.S. regulations

  • OSHA 29 CFR 1910.107: spray finishing using flammable and combustible materials
  • OSHA 29 CFR 1910.94: ventilation, including abrasive blasting
  • EPA 40 CFR Part 63 Subpart MMMM: NESHAP for surface coating of miscellaneous metal parts and products

Frequently asked questions

How do I calculate paint coverage?

Theoretical coverage = 1,604 × volume solids ÷ dry film in mils, in ft²/gal. A 60% solids paint at 3 mils covers about 321 ft²/gal; with 25% airless loss and a medium blast profile, practical coverage drops to about 190 ft²/gal.

What wet film gives 5 mils dry?

Divide by the solids fraction and add thinning: at 80% solids with 5% thinner, the wet film should be about 6.6 mils.

How much paintable area is in a ton of steel?

Medium shapes run 250 to 350 ft² per short ton; a W8×31 has about 250 ft²/ton and light angles exceed 440 ft²/ton.

What thickness for an industrial environment?

For C4 with high durability (15 to 25 years), epoxy and polyurethane systems usually total 9.5 to 11 mils. Check the ISO 12944-5 tables and the manufacturer.