Stainless Steel vs Aluminum vs Copper Evaporator Coils: CSTHEATEXCHANGER's Material Guide for Choosing the Right Coil

There is no single best evaporator coil material. Copper tube with aluminium fin is the default for most air-conditioning and refrigeration duty because of its heat transfer and manufacturability. All-aluminium coils are lighter, cheaper, recyclable and immune to the formic-acid (formicary) corrosion that attacks copper, which is why they have taken over much of the standard AC and freezer market. Stainless steel tube coils cost more and transfer heat less readily, but they are the only choice where the fluid or the environment attacks copper and aluminium — deionized water, laser cooling, food processing washdown, salty or chemically aggressive air. CSTHEATEXCHANGER manufactures all three and selects the material from the fluid, the air, the temperature range and the budget — never from habit.

Comparison at a glance

Copper tube / aluminium fin — the CSTHEATEXCHANGER default

• Standard tube programme: 5, 7, 9.52, 12.70 and 15.87 mm OD; plain or rippled tube; multiple wall thicknesses.

• Fins: 8006 H22 aluminium; flat, corrugated or louvred; hydrophilic, hydrophobic or gold-epoxy coating; pre-coated anti-corrosion aluminium or copper fins for aggressive sites.

• Tubes expanded for full fin contact and efficient thermal exchange.

• Choose it when: standard HVAC/refrigeration duty, highest capacity per face area, easy field repair.

All-aluminium coils — lighter, cheaper, formic-acid proof

From our All Aluminum Heat Exchanger page:

• Cheaper, lighter, recyclable.

• Better corrosion resistance because the material balance is better (single metal).

• Resistance to formic acid corrosion — formic acid corrosion only occurs in copper-based alloys; aluminium is not affected. Replacing copper with aluminium reduces raw material cost and warranty cost.

• Withstands –40 °F to 180 °F (–40 °C to 82 °C): suitable for cold storage and high-temperature industrial use.

• Our aluminium tube coils fit about 95 % of standard AC units, freezers and refrigeration equipment; custom sizes offered.

• Choose it when: weight, cost or formicary corrosion is the driver; standard AC and freezer replacement.

Stainless steel tube coils — for fluids and air that attack everything else

From our Stainless Steel Tube Heat Exchanger page:

• Tube: stainless steel 304, 310, 316, 254 SMO, Inconel and additional options; sizes 7 mm to 15.88 mm.

• Fin: aluminium, coated aluminium, copper or stainless steel (316L for food-sector or salty environments).

• Applications: laser cooling, deionized water, fuel cells, hot gas cooling, high-corrosive gases, gas-to-gas and gas-to-liquid.

• Products: Stainless Steel Tube Heat Exchanger, Stainless Steel Cooling Coil.

• Choose it when: the fluid is DI water or chemically aggressive; the air is salty, acidic or washed down; or the temperature is beyond copper and aluminium limits.

How CSTHEATEXCHANGER selects the material for your coil

1. Fluid inside the tubes — refrigerant, water, glycol, DI water, chemical, gas. DI water or chemicals → stainless.

2. Air or gas over the fins — clean indoor, outdoor coastal, food washdown, acidic process. Aggressive → coated fins, copper fins or 316L SS fins.

3. Environment history — if existing copper coils have failed from pinhole leaks with no obvious cause, formicary corrosion is likely → all-aluminium.

4. Temperature range — within –40 °C to 82 °C, all three work; above, stainless.

5. Weight and cost targets — all-aluminium where these dominate.

6. Capacity per face area — copper where the coil must be as compact as possible.

We state the recommended material and the reason on the drawing we send for approval.