---
title: "Powder Coating Spec: Chemistries, Thickness, Finish | OpenSpindle"
description: "Powder coating spec guide: polyester, epoxy, hybrid, and polyurethane chemistries compared by durability, UV resistance, thickness, and finish options."
canonical: https://openspindle.com/reference/powder-coating-spec
---

# Powder Coating Spec Guide

Polyester, epoxy, hybrid, and polyurethane powders compared by durability, UV resistance, film thickness, and finish, so you can spec a coating that holds up in service.

Powder coating is a dry finishing process: electrostatically charged polymer powder is sprayed onto a grounded part, then cured with heat so it flows into a tough, uniform film. The powder chemistry controls how it performs. Polyester is the workhorse for outdoor and UV-exposed parts; epoxy is the tough, chemical-resistant indoor finish; epoxy-polyester hybrid splits the difference for indoor use; polyurethane gives a smooth, weather-resistant cosmetic finish. Typical film thickness runs about 2 to 4 mils (50 to 100 microns).

## Powder chemistries compared

The biggest split is indoor vs outdoor. Any epoxy content chalks and degrades quickly under UV, so epoxy and hybrid powders are for indoor service; polyester and polyurethane hold color and gloss outdoors.

| Chemistry | UV / outdoor | Durability | Typical use |
| --- | --- | --- | --- |
| Polyester (TGIC / TGIC-free) | Good; UV stable | Good weathering and corrosion | Outdoor and general-purpose parts, architectural, enclosures |
| Epoxy | Poor; chalks in sunlight | Excellent hardness, adhesion, chemical resistance | Indoor parts, rebar, appliances, chemical exposure |
| Epoxy-polyester hybrid | Poor to fair; not for exterior | Good toughness and corrosion resistance | Indoor decorative parts, office furniture, shelving |
| Polyurethane | Very good; weather resistant | Excellent flow and cosmetic finish, good chemical resistance | Cosmetic outdoor parts where smoothness matters |

*For maximum exterior color and gloss retention, super-durable polyester or fluoropolymer (FEVE) powders outperform standard polyester; confirm the grade with your coater.*

## Film thickness and finish options

Most powder coats are specified around 2 to 4 mils. Thinner films (roughly 1.5 to 2.5 mils) suit smooth cosmetic parts; thicker builds add durability and hide substrate texture. Powder can be gloss, semi-gloss, matte, or textured.

| Property | Typical range | Notes |
| --- | --- | --- |
| Film thickness | 2-4 mil (50-100 um) | Thicker on functional parts; thinner on cosmetic surfaces |
| Gloss | Flat to high gloss | Measured at 60 degrees; flat hides defects, gloss shows them |
| Texture | Smooth, fine, or coarse texture | Texture hides substrate imperfections and adds scuff resistance |

## Pretreatment matters

Powder coating adhesion and corrosion resistance depend on surface prep, not just the powder. Parts are typically cleaned and degreased, then given a conversion coating: iron or zinc phosphate on steel, or a chromate or newer chrome-free treatment on aluminum. Blasting adds a mechanical profile. Skipping pretreatment is the most common cause of premature failure such as edge creep and flaking.

## Powder coat vs anodizing on aluminum

On aluminum, powder coating and anodizing solve different problems. Powder coating builds a colored film on top of the metal and works on almost any alloy and casting, giving a wide color range and thicker corrosion protection, but it can chip. Anodizing converts the surface into an integral oxide that will not chip or peel and holds tight tolerances, but the color palette is narrower and quality is alloy-dependent. Choose powder for bold color and coverage on mixed alloys; choose anodizing for a hard, thin, integral finish on wrought aluminum.

Values reflect common powder-coating practice; adhesion and corrosion life depend heavily on pretreatment and substrate. Confirm chemistry, thickness, gloss, and pretreatment with your coater before release.

## On OpenSpindle

- [Powder coating capability](https://openspindle.com/capabilities/powder-coating.md)
- [Anodizing spec chart](https://openspindle.com/reference/anodizing-spec.md)
- [Surface finishes compared](https://openspindle.com/reference/surface-finishes-compared.md)

## Frequently asked questions

### Can powder coating be used outdoors?

Yes, if you pick the right chemistry. Polyester and polyurethane powders are UV stable and hold color and gloss outdoors. Epoxy and epoxy-polyester hybrid powders chalk and fade quickly in sunlight and should stay indoors. For long exterior color retention, ask for super-durable polyester or fluoropolymer powder.

### How thick is a typical powder coat?

Most powder coats land around 2 to 4 mils (50 to 100 microns). Thinner films of roughly 1.5 to 2.5 mils are used on smooth cosmetic parts, while thicker builds add durability and hide substrate texture. Very tight-tolerance features may need masking because the film adds dimension.

### What is the difference between epoxy and polyester powder coating?

Epoxy powders are extremely tough and chemical resistant but degrade under UV, so they are for indoor parts. Polyester powders are UV stable and weather well, making them the standard choice for outdoor and general-purpose parts. Epoxy-polyester hybrids blend both but are still indoor finishes.

### Should I powder coat or anodize aluminum?

Powder coat when you want bold color, thicker coverage, or a finish that works across mixed alloys and castings. Anodize when you need a hard, thin, integral surface that will not chip or peel and holds tight tolerances. Anodizing has a narrower color range and is more alloy-dependent.