Powder Coating for Coastal Projects: Qualicoat, AAMA 2603/2604/2605 and Salt Spray Explained
How to specify powder coating on architectural aluminium for marine and coastal exposure — what the Qualicoat and AAMA classes mean, and why pre-treatment matters more than the coating.
Short answer: on a coastal project, the coating class you specify decides whether the aluminium still looks acceptable in ten years — and the pre-treatment underneath decides whether it corrodes at all.
The two standards you will meet
AAMA 2603 / 2604 / 2605
| AAMA 2603 | AAMA 2604 | AAMA 2605 | |
|---|---|---|---|
| Tier | Entry | Intermediate | High performance |
| Chemistry | Standard polyester | Enhanced polyester | Fluoropolymer (70% PVDF) |
| Suits | Interior, sheltered | Most commercial exterior | Coastal, high-rise |
Pre-treatment: the part that actually prevents corrosion
The coating provides colour, gloss and UV durability. It does not, by itself, stop corrosion at the interface.
What actually fails, and in what order
- Filiform corrosion from cut edges and fixings.
- Gloss loss and chalking — the polyester binder degrading under UV.
- Colour drift — some pigments fade faster.
- Galvanic attack at dissimilar-metal contacts.
What to ask any supplier
- "What class, and to which current revision?"
- "Is the coating plant licensed and audited?"
- "What pre-treatment system?"
- "What is the warranty?"
- "How are post-coating cuts treated?"
- "What exposure data exists?"
- "How is galvanic isolation handled?"
Written by the engineering team at GRAND HOMEDECOR (Guangdong Grand Homedecor Technology Co., Ltd.).
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