The Powder Coat That Chipped (Poor Prep)
We powder-coated a steel bracket (a machine guard, article 74). On the floor, the coat chipped (it peeled off). The problem: the surface prep (the steel was oily, from machining). The powder (a dry paint) didn’t stick (the oil prevented adhesion). We re-prepped (cleaned the part, with a solvent, before coating). The coat stuck (it didn’t chip). The mistake was skipping the prep (the oil was on the surface).
Powder coating — the process and the prep. This article covers the basics.
What is Powder Coating?
Powder coating is a dry finish (a powder, electrostatically applied). The part is prepped (cleaned), the powder is sprayed (electrostatically attracted to the part), and the part is cured (baked, in an oven). The powder melts (and cures) into a hard coat. Durable (better than wet paint).
Step 1: The Prep (Critical)
The prep is the key. The part must be clean (no oil, no rust). A dirty part (oily) doesn’t take the powder (it chips). The prep: a solvent wipe (or a wash, a phosphate). The part is clean (the powder sticks). The prep is 80% of the quality (a good coat needs a clean part).
The powder coat rule: Prep is critical. The coat that chipped was on an oily part. Clean the part (solvent, or wash). The powder sticks (on a clean surface). Don’t skip the prep (the oil kills it).
Step 2: The Pretreatment (Phosphate)
For a corrosion-resistant part (outdoor, or wet), use a phosphate pretreatment (a zinc phosphate). It converts the surface (it promotes adhesion, and corrosion resistance). For an indoor part (dry), a solvent wipe is enough.
Step 3: The Cure (Oven)
After spraying, the part goes in an oven (cured, at 180–200°C, for 15–30 min). The powder melts (and flows) into a coat. An under-cured part (not hot enough) is soft (it scratches). An over-cured part (too hot) is brittle. Follow the powder’s cure schedule (the manufacturer’s spec).
Step 4: The Color (Texture)
The powder comes in colors (and textures). A smooth (glossy) finish. A textured (orange-peel) finish (for a rugged look). Choose the color (and texture). The powder is durable (it’s hard, chip-resistant).
| Step | Process |
|---|---|
| Prep | Clean (solvent, or phosphate) |
| Spray | Electrostatic powder |
| Cure | Oven (180°C, 20 min) |
| Finish | Durable (chip-resistant) |
A Powder Coat Checklist
- Is the part clean? (No oil?)
- Is it prepped? (Solvent? Phosphate?)
- Is the powder applied? (Even?)
- Is it cured? (Oven? Right temp?)
- Is the color right? (Texture?)
- Does it chip? (Adhesion?)
- Is it corrosion-resistant? (Phosphate?)
- Is the part racked? (For spray?)
- Is the masking done? (Threads?)
- Is the cost right? (Volume?)
The Bottom Line
Powder coating is a durable finish (if prepped right). The coat that chipped was on an oily part. Clean the part (prep). Cure (oven). The coat that didn’t chip wasn’t the best powder — it was prepped.
