Industrial Powder Coating Specification: A Buyer’s Checklist

Start with the part and its service environment

Identify the base metal and grade, fabrication state, dimensions, weight, quantity, drawing revision and any existing finish. State whether the part will live indoors, outdoors, near road salt or in a washdown area. Include expected contact with chemicals, UV, abrasion and heat. Those conditions guide system selection; colour alone cannot.

For assemblies, identify welds, cut edges, crevices, drainage points and surfaces that will be inaccessible after installation. Send photos and a drawing rather than asking the coater to infer critical faces.

• Substrate and fabrication method
• Service exposure and expected life
• Critical cosmetic and functional surfaces

Define the coating system, not just the finish

Specify the required preparation or performance outcome, approved primer and topcoat if applicable, colour and gloss tolerance, and a dry film thickness range at defined measurement locations. Confirm whether the powder manufacturer's cure schedule is based on part metal temperature rather than oven air temperature. A heavy part and a thin coupon can reach cure at different times.

Discuss sharp edges, hollow sections, threads, grounding points and mating surfaces early. Masking and racking decisions affect coverage, fit and cost. Do not assume that every cavity can be coated by electrostatic spray.

• Pretreatment and surface condition
• Coating chemistry and appearance
• Masking, racking, film build and cure

Make inspection and documentation explicit

Name the test method, sampling plan, acceptance criterion and who receives the results. A standard number by itself does not establish a pass mark. Decide whether the job needs thickness readings, adhesion checks, visual criteria or qualification panels. Specify treatment of touch-ups and nonconforming parts before production starts.

For repeat orders, agree on a first article, retained reference sample and revision control. This is particularly valuable where the coating changes the fit of holes, tabs or electrical interfaces.

RFQ shortcut: attach the drawing, annual volume, exposure, coating target and the tests you will use to accept the work.

Technical references

The Powder Coating Institute defines pretreatment and film build in its glossary. ASTM D7091 addresses dry film thickness measurement; the test method and acceptance limits still need to be selected for the actual project.