Bare (mill finish)
Degreased foil without coating. Lowest cost and the right choice for condensers in clean, dry air and for coils that will receive a post-coating after assembly.
HVAC fin stock guide
Air Conditioner Aluminium Foil (Fin Stock)
Air conditioner foil is thin aluminium strip, usually 0.09 – 0.15 mm thick, that is stamped into the fins of evaporator and condenser coils. The common grades are 8011, 1100, 1200, 3102 and 8006 in H22 to H26 tempers, supplied bare or with a hydrophilic or anti-corrosion coating. This guide explains how to choose the alloy, temper, gauge and coating, and what to specify when you order.
- Alloys
- 8011, 1100, 1200, 3102, 8006
- Tempers
- O, H22, H24, H26
- Thickness
- 0.08 – 0.20 mm
- Coatings
- Bare, hydrophilic, epoxy, hydrophobic
What air conditioner foil does in a coil
In a fin-and-tube heat exchanger, refrigerant runs through copper or aluminium tubes and the fins multiply the surface area that touches the air. Fins typically provide 80 – 90 % of the heat-transfer surface of a residential split-unit coil, so the foil they are made from has a direct effect on cooling capacity, energy efficiency and service life.
Fin foil is not ordinary packaging foil. It is rolled to a tight gauge tolerance, annealed to a specific temper so that it can be drawn into collared fins in a high-speed progressive press, and often coated on both sides before slitting. The fin press punches holes, pulls up collars that grip the tube, adds louvres or waves to break up the air boundary layer, and cuts the strip into fin packs at several hundred strokes per minute. Foil that is too hard cracks at the collars; foil that is too soft tears or forms uneven collar heights, which leaves gaps between tube and fin and reduces heat transfer.
Besides fins, the same family of thin aluminium products appears elsewhere in an air conditioning system: foil-faced duct insulation, aluminium foil tape for sealing joints, flexible foil ducting, and laminated vapour barriers. Those uses need softer, cheaper foil and are covered briefly further down this guide.
Aluminium alloys used for air conditioner fins
All fin alloys are non-heat-treatable. Their strength comes from cold rolling, partial annealing and, in 3xxx and 8xxx grades, from manganese or iron-rich particles. The table summarises where each one fits; nominal compositions follow the Aluminum Association registrations and EN 573-3.
| Alloy | Main alloying elements | Strength level | Typical use in AC systems |
|---|---|---|---|
| 1100 / 1200 | ≥ 99.0 % Al, small Cu (1100), Fe + Si | Low | Fins needing very high formability and thermal conductivity; small evaporators |
| 1050 / 1060 / 1030B | ≥ 99.3 – 99.6 % Al | Lowest | Thin fins in soft tempers, foil for insulation facing |
| 8011 | Fe 0.6 – 1.0 %, Si 0.5 – 0.9 % | Low–medium | The default general-purpose fin alloy for split units and window units |
| 3102 | Mn 0.05 – 0.40 % | Medium | Fins where good strength and better corrosion behaviour than 8011 are wanted |
| 8006 | Fe 1.2 – 2.0 %, Mn 0.3 – 1.0 % | Medium–high | Thin high-strength fins; lets designers reduce gauge without losing fin stiffness |
| 7072 | Zn 0.8 – 1.3 % | Low | Sacrificial fins or cladding that corrode in preference to the tube |
| Brazing composites (4343/3003/4343, 4343/3003/4045) | Al-Si cladding on a 3003 core | Medium | Brazed all-aluminium coils, condensers and automotive heat exchangers |
8011 dominates the market because it balances cost, formability and strength: the iron and silicon particles refine the grain and give more strength than 1xxx foil at the same temper, while the alloy still rolls easily to thin gauges. Designers who need to cut weight or material cost move to 8006 or 3102 so they can roll the fin thinner, and buyers of fins for all-aluminium brazed microchannel or round-tube coils use clad brazing foil instead. For the 8011 grade alone, see our dedicated 8011 air conditioner foil guide.
Tempers and mechanical properties for fin foil
Fin foil is supplied in partially annealed H2x tempers. The foil is cold rolled to gauge and then given a controlled back-anneal so that strength drops to a target band while elongation rises. Choosing the temper is about matching the fin press: collar height, collar style (single, double or reflare), fin pitch and louvre geometry all change how much stretch the foil must survive.
| Temper | Condition | Strength / ductility balance | Best suited to |
|---|---|---|---|
| O | Fully annealed | Lowest strength, highest elongation | Duct foil, tape backing, very deep collars |
| H22 | Strain hardened, partially annealed (quarter hard) | Low strength, high elongation | High collars, reflared collars, wide fin pitch |
| H24 | Strain hardened, partially annealed (half hard) | Medium strength, moderate elongation | Standard flat or louvred fins |
| H26 | Strain hardened, partially annealed (three-quarter hard) | Higher strength, lower elongation | Thin fins with low collars where stiffness matters |
Guaranteed tensile, proof and elongation limits depend on alloy, gauge and the order standard (EN 683-2, GB/T 3198 or the customer specification); they are printed on the mill certificate for every lot. Ask for the limits of the exact alloy, temper and gauge you are buying rather than relying on generic figures.
Two further properties matter in practice. Erichsen cup height (or a similar cupping test) predicts how well the foil will form a collar without splitting; many fin makers include a minimum cup value in their purchase specification. Thermal conductivity falls as alloy content rises: commercially pure 1100 sits around 220 W/m·K, and alloys with more iron and manganese, such as 8011 and 8006, are somewhat lower. In a fin the difference is small compared with the effect of fin geometry and air-side fouling, which is why higher-strength alloys are worth the minor loss.
Bare, hydrophilic, hydrophobic and corrosion-resistant fin foil
Hydrophilic coated
A thin water-loving film, often over a corrosion-resistant primer, makes condensate spread into a film instead of beading. Water drains faster, air passages stay open, and the coil runs quieter with less carry-over. Most evaporator fins for split air conditioners now use it.
Hydrophobic coated
The opposite approach: water beads and rolls off. Used where frosting and defrost cycles matter, for example in heat pump outdoor coils, so that melt water leaves the fins quickly.
Epoxy / anti-corrosion
A thicker organic coating, frequently gold or blue tinted, protects fins against salt air, industrial pollution and acidic condensate. Specified for coastal installations and rooftop units.
Self-lubricating
A coating with built-in lubricity lets the fin press run with little or no evaporative oil, reducing degreasing and VOC emissions at the coil plant.
Antibacterial
Coatings with antimicrobial agents limit mould and bacterial growth on wet evaporator fins, which helps indoor air quality.
When comparing coated foils, ask for test data rather than colour. Useful acceptance criteria include the initial water contact angle (hydrophilic coatings typically target 10 – 20° or lower), the contact angle after repeated wet-dry cycling, neutral salt-spray performance to ISO 9227 or ASTM B117, coating weight in g/m², adhesion after cupping, and resistance to the stamping oils used in your press. A coating that starts at a low contact angle but loses hydrophilicity after a few weeks of condensate exposure delivers none of the benefit. Our hydrophilic lacquered foil purchasing guide covers these tests in more depth.
Typical supply range for air conditioner foil
Fin foil supply range
- Alloys
- 1050, 1060, 1100, 1200, 3102, 7072, 8006, 8011; clad brazing foil on request
- Tempers
- O, H22, H24, H26 (H18 for some brazing foil)
- Thickness
- 0.08 – 0.20 mm; most orders between 0.095 and 0.15 mm
- Thickness tolerance
- Typically ±3 – 5 % of nominal, tighter on request
- Width
- Slit coils from about 50 mm up to 1,650 mm master width
- Core inside diameter
- 75 mm, 150 mm, 200 mm or to your decoiler
- Coil outside diameter
- To suit the fin press decoiler; agree maximum coil weight in advance
- Surface
- Degreased bare, hydrophilic (blue, gold, colourless), epoxy, hydrophobic
- Standards
- EN 683-1/-2/-3, EN 546, EN 573-3, GB/T 3198, JIS H4160, or customer specification
Slit width tolerance, burr height, camber and coil joints should be stated on the order because they affect press uptime.
Quality points that keep the fin press running
Most fin-line stoppages trace back to a handful of foil defects. A good purchase specification names each one and the method used to check it.
| Property | Why it matters | How it is checked |
|---|---|---|
| Gauge uniformity | Uneven thickness changes collar height and fin pitch | Contact or X-ray gauge along and across the coil |
| Mechanical properties | Too hard cracks collars; too soft tears and wrinkles | Tensile test and cupping test per lot |
| Surface cleanliness | Residual rolling oil affects coating adhesion and brazing | Wettability (dyne) or water-break test |
| Flatness and camber | Wavy edges or camber cause misfeeds and fin skew | Visual on a flat table, camber over a set length |
| Pinholes | Weak spots split during collar drawing | Light-table inspection |
| Slit edge burr | Burrs damage tooling and cut operators | Edge inspection, burr height measurement |
| Coating weight and adhesion | Thin or poorly bonded coatings fail early | Gravimetric coating weight, adhesion after cupping |
| Coil build | Telescoping or loose wraps damage foil in transit | Visual check before packing |
Each Metline shipment includes a mill test certificate to EN 10204 3.1 reporting chemistry, mechanical results and gauge for the lot, with coating data for coated foil.
Other aluminium foil products in air conditioning
- Foil-faced duct insulation: 1235 or 8011 O-temper foil, often reinforced with glass scrim and laminated to kraft paper, forms the vapour barrier on duct wrap and duct board
- Aluminium foil tape: soft foil, 30 – 80 µm, with acrylic or rubber adhesive seals duct joints and insulation seams; see our foil tape guide
- Flexible ducts: laminated foil helically wound over a steel wire forms flexible air ducts for ceilings and branch connections
- Refrigerant pipe insulation jacketing: embossed foil or thin sheet protects insulation on outdoor line sets
- Brazed heat exchangers: clad brazing foil and strip form the fins of all-aluminium condensers and microchannel coils; see brazing foil
These products use softer tempers and looser tolerances than fin stock, and the alloy choice is driven mostly by cost and lamination performance rather than formability in a press.
How to choose air conditioner foil: step by step
- Start from the fin dieCollar height, collar type and fin pitch set the minimum elongation. Ask your die maker or press supplier for the temper the tooling was designed around.
- Pick the alloy for gauge and cost8011 suits most fins at 0.10 – 0.12 mm. If you want to go thinner, compare 8006 or 3102, which keep fin stiffness at lower gauge.
- Match the coating to the coilEvaporators that run wet benefit from hydrophilic coating. Outdoor coils near the sea or in polluted air need anti-corrosion coatings. Dry condensers in clean air can run bare.
- Define the coil formatSlit width, core ID, maximum outside diameter and coil weight must match your decoiler and handling equipment.
- Set acceptance testsTensile and cupping values, gauge tolerance, coating weight, contact angle and salt-spray performance.
- Run a trial coilBefore a large order, press a trial coil on the production die and record collar cracking, tool wear and coating flaking.
References and standards
- EN 683-1/-2/-3 – Aluminium and aluminium alloys: Finstock (inspection, mechanical properties, tolerances)
- EN 546 – Aluminium and aluminium alloys: Foil
- EN 573-3 – Chemical composition and form of wrought products
- ISO 9227 – Corrosion tests in artificial atmospheres: salt spray tests
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits
Air conditioner aluminium (aluminum) foil: frequently asked questions
Which aluminium alloy is best for air conditioner fins?
8011 is the most common choice because it combines low cost, good formability and adequate strength. 1100 and 1200 give the highest formability, while 8006 and 3102 are stronger and let you roll thinner fins.
What thickness is air conditioner fin foil?
Most room and split air conditioners use 0.095 – 0.12 mm foil. Larger commercial coils use 0.13 – 0.20 mm. Thinner foil saves material but needs a stronger alloy or temper to keep fins rigid.
What is the difference between H22, H24 and H26 fin foil?
All three are cold rolled and partially annealed. H22 is the softest and best for high collars, H24 is the general standard, and H26 is harder for thin fins with low collars. The right choice depends on your fin die.
Why is hydrophilic fin foil used on evaporators?
Evaporator fins collect condensate. A hydrophilic coating spreads water into a thin film that drains quickly, so the air passages stay open, airflow resistance and noise drop, and condensate is less likely to be blown into the room.
Is blue or gold fin foil better?
The colour only identifies the coating; it says nothing about performance. Compare coating type, coating weight, contact angle durability and salt-spray results instead.
Can aluminum fin foil be used with copper tubes?
Yes, aluminium fins on copper tubes is the standard construction. In corrosive or coastal air, use coated fins or a post-coating to slow galvanic corrosion at the fin-to-tube contact.
Need fin foil for your coil line?
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