Both finishes protect steel from corrosion. They do it in different ways, they suit different environments, and mixing them up on the wrong part means paying for protection you don't need — or under-protecting one you do.
Powder coating: color, finish, and moderate protection
Powder coating applies a dry pigmented powder electrostatically, then cures it under heat into a hard, even coating — typically 60–120 microns thick. It comes in any RAL color, gives a consistent cosmetic finish, and provides solid protection for parts that live indoors or under moderate outdoor exposure.
What it doesn't do well is protect bare edges, weld seams with pinholes, or scratched-through areas — powder coat is a surface film, and once it's breached, the steel underneath is exposed same as if it had no coating at all.
Galvanizing: sacrificial protection that keeps working after damage
Hot-dip galvanizing coats steel in zinc, which protects two ways: as a physical barrier, and — critically — sacrificially. If the coating gets scratched, the surrounding zinc corrodes preferentially and protects the exposed steel underneath, rather than letting rust start at the scratch. That's why galvanizing is the standard choice for parts that will scrape, impact, or sit outdoors for years with no repainting: structural steel, outdoor frames, agricultural and construction equipment.
The tradeoff is cosmetic: galvanizing has a limited color range (mostly the natural zinc finish) and a rougher surface than powder coat.
When parts need both
Powder coat over galvanized steel ("duplex" coating) combines both: the zinc layer keeps protecting even if the powder coat is damaged, and the powder coat adds color and a smoother cosmetic finish on top. It costs more than either alone, and it's usually reserved for parts that need to look finished and survive heavy outdoor exposure — exterior cabinets, equipment that will be handled roughly, anything under a multi-year warranty in the field.
A quick decision guide
| Situation | Recommended finish |
|---|---|
| Indoor part, needs a specific RAL color | Powder coating |
| Outdoor structural steel, impact-prone | Galvanizing |
| Outdoor equipment that must look finished for years | Powder coat over galvanizing |
| Aluminum parts | Powder coating (galvanizing doesn't apply to aluminum) |
What this means for your spec
If you're not sure which your part needs, the deciding question is usually: what happens when the coating gets scratched? If the answer is "it needs to keep protecting the steel underneath," you need zinc under whatever's on top.
See our powder coating service page for thickness and material notes, or request a quote with your finish requirements.