Blue Fin Coil Treatment
1. What is Blue Fin?
Blue Fin is an aluminium outdoor-unit heat-exchanger fin with additional surface coatings provided for anti-corrosion purposes.
The outdoor coil must remain exposed to moving air so the system can absorb and reject heat. Because the aluminium fins are thin and exposed to the environment, corrosion can damage the fin surface and reduce the coil's ability to transfer heat effectively.
The Blue Fin treatment adds protective coating layers to the aluminium fin to improve corrosion resistance and help maintain the condition of the heat exchanger over time.
2. Blue Fin coating layers
The technical information describes a three-layer coating structure applied over the aluminium base material.
| Layer | Purpose | Reference coating mass |
|---|---|---|
| Resin hydrophilic layer | Maintains a long-lasting hydrophilic effect on the heat-exchanger surface and assists water behaviour across the fin surface. | 100-400 mg/m² |
| Resin corrosion-resistant layer | Protects the aluminium fins against corrosion and is the layer that gives Blue Fin its characteristic blue appearance. | Technical references show coating ranges that vary by document/test sample. |
| Chromate corrosion-resistant layer | Provides chromate treatment to the aluminium fin to further resist corrosion. | Cr: 10-40 mg/m² |
3. Why corrosion protection matters
The outdoor heat exchanger is a key part of the refrigeration cycle. Air must pass through the aluminium fins while refrigerant travels through the coil tubing.
- Corrosion can progressively damage or remove aluminium fin material.
- Damaged fins reduce the effective heat-transfer surface of the coil.
- Reduced heat-transfer performance can adversely affect system capacity and efficiency.
- Corrosive environments, including salt-laden coastal air, can accelerate deterioration.
Blue Fin is intended to improve the corrosion resistance of the heat-exchanger fins and slow this deterioration compared with untreated aluminium fins.
4. Manufacturer salt spray testing
Fujitsu General carried out in-house corrosion testing using a salt spray test based on JIS Z2371. Bare aluminium fins and corrosion-proof Blue Fin samples were examined after 100, 200, 500 and 1,000 hours.
| Test point | Bare aluminium fin | Blue Fin |
|---|---|---|
| 500 hours | The test report records that 2 or 3 fins from both sides had dropped away due to electrolytic corrosion. | The Blue Fin sample remained substantially intact in the supplied test photographs. |
| 1,000 hours | The report records 7 or 8 fins from both sides had dropped away due to electrolytic corrosion and the fin surface was heavily corroded by salt. | Only a few fins from both sides were reported as corroded, no fins had dropped away, and the surface condition was described as good. |
5. How to confirm whether a model has Blue Fin
Do not rely on colour alone when confirming a model specification. For a specific outdoor unit, check the applicable Technical Manual.
Outdoor Unit Specifications → Heat Exchanger → Fin Type / Surface Treatment
If Blue Fin applies to the model, it should be identified in the surface-treatment information for the heat exchanger.
6. Installation and maintenance considerations
- Blue Fin improves corrosion resistance but does not remove the need for correct installation and routine maintenance.
- Keep the outdoor heat exchanger clean and free from accumulated salt, dirt and contaminants.
- Do not assume Blue Fin provides equivalent corrosion protection to the cabinet, electrical components, PCB assemblies or all other outdoor-unit parts.
- In aggressive coastal or industrial environments, additional site-specific protection and maintenance may still be required.
- When assessing corrosion-related performance or warranty concerns, consider the installation environment and the condition of the complete outdoor unit, not the coil alone.