Is Gold Fin or Blue Fin Enough for Coastal Sites?
Key facts
| Part of the coil | Gold or blue fin | Post-fabrication coating |
|---|---|---|
| Flat fin faces | Covered | Covered |
| Cut fin edges | Bare | Covered |
| Fin collars | Little or none | Covered |
| Copper tubes and bends | Bare | Covered |
| Brazed joints | Bare | Covered |
What gold and blue fin are
Both are aluminium fin stock coated at the mill, typically with a hydrophilic or epoxy-based layer. The colour identifies the product, not its corrosion resistance. The fins are then stamped, collared and expanded onto the tubes.
Where the protection stops
Stamping cuts through the coating at every fin edge and hole. Collars are formed after coating, and the copper tubes, return bends and brazed joints were never coated. On a Cu-Al coil the collar is where copper and aluminium meet — the point where coastal corrosion begins.
When it is enough
Inland sites in C2 or C3 without industry, and evaporators where hydrophilic fin helps drainage.
What this means for your project
If a supplier offers gold fin for a coastal project, ask what protects the collars, tubes and joints. For C4 and C5 sites, specify a post-fabrication coating on the whole coil.
