Aluminum Foil Sleeve Oxidation and Delamination
Foil faced sleeves age. The reflective face dulls, powders or lifts away from the core, and a sleeve specified for radiant duty quietly stops shielding. The question on site is always the same: keep it, or replace it.
Why the foil face changes
- Heat cycling oxidises the aluminium. A dull grey-white face has higher emissivity than a bright one, so less radiation goes back toward the source.
- Water and salt held against the face drive corrosion, which is why outdoor runs and wash down areas age faster.
- Abrasion and dents break the flat reflective surface. A creased face reflects less even when the foil is continuous.
- Baked on oil, dust and overspray raise emissivity for the same reason oxide does.
Keep it or replace it
| Observation | What it means | Action |
|---|---|---|
| Uniform dulling, no lifting | Surface oxide, sleeve intact | Note it and re-inspect at the next service |
| White powder on the face | Aluminium corrosion product | Clean, check whether the foil has thinned, replace if it has |
| Foil lifting off the core layer | The bond between foil and core has failed | Replace the sleeve |
| Cracks or splits at bends | Mechanical fatigue at the bend | Replace and re-check the bend radius |
| Water inside the sleeve | Core wetting, insulation performance collapses | Dry and re-close the ends, or replace |
| Foil torn through at a clamp | Local damage from the fixing | Replace the section and add a wrap |
How to make the next one last
- Keep the gap. Reflection needs clearance, so fit the sleeve so the foil face does not rest on the hot line.
- Close the ends. Band clamps or stainless ties over the foil stop water reaching the core.
- Protect the face at bends. Re-check the bend radius and add a wrap where the foil creases.
- Watch the fixings. A clamp that bites through the foil creates the corrosion start point.
- Inspect on the same cycle as the equipment, and record what the face looked like last time.
About the temperature figure
Our own product page holds the catalogue figure of 1000°C short term until its test basis is published. Aluminium melts near 660°C, so a number above that describes one test geometry rather than a working contact rating. Design against the continuous rating when it is issued, and treat the foil as a reflector rather than a contact barrier.
If a run needs a verified thermal rating, a sleeving qualified to a published standard is a different procurement route. UL 1441 recognition or an ASTM D2671 test basis puts the number on a document you can check.
What to send
Send the pipe OD, the environment, how long the sleeve has been in service and what the face looks like now. We return the replacement build and the fixing set.
Frequently asked questions
Is a dull foil face a fault?
Not on its own. Uniform dulling is surface oxidation and the sleeve still shields. Lifting, cracking, powdering or water inside is the point at which it should be replaced.
Can I clean the foil face and keep the sleeve?
Clean oxide and contamination off by hand if the foil is intact, then check whether the surface is still flat. Once the foil has thinned or torn, cleaning does not restore reflection.
Why did the outdoor sleeve fail in a year when the indoor one lasted several?
Water and salt held against the foil accelerate corrosion. Outdoor runs also collect contamination that bakes onto the face. Both raise emissivity.
Does a scuff matter if the foil is not torn?
It does. Reflection depends on a smooth low-emissivity surface, and a scuffed or dented face reflects less even when the metal is continuous.
Should I just specify a higher temperature sleeve?
Only against a verified rating for the duty you actually have. A higher advertised number without a test basis does not protect the run.