Heat Exchanger Material Selection: Stainless Steel vs Aluminum vs PP Polymer
Heat Exchanger Material Selection: Stainless Steel vs Aluminum vs PP Polymer
The single most important purchasing decision after core type is the plate material. It decides how long the air-to-air heat exchanger lasts, what temperature and corrosiveness it can survive, and what it costs. The three materials that cover 95% of HVAC and industrial duties are stainless steel, aluminum, and polypropylene (PP) polymer. This guide compares them so you can specify with confidence.
The Three Materials at a Glance
| Property | Stainless steel | Aluminum | PP polymer |
|---|---|---|---|
| Max continuous temp | 300°C+ (grade-dependent) | ~150°C (softens higher) | ~70–80°C |
| Corrosion resistance | Excellent (acid/flue gas) | Good (needs coating for wet) | Excellent (chemical/erosive) |
| Thermal conductivity | Moderate | High | Low |
| Weight | Heavy | Light | Very light |
| Cost | Highest | Medium | Low |
| Typical use | Flue gas, kiln, corrosive | HVAC, AHU, fresh air | Chemical/erosive exhaust |
Stainless Steel — When You Need to Survive Heat and Corrosion
Choose stainless (commonly 304 or 316L) when the airstream is hot, acidic, or laden with condensate and particulates: boiler and kiln waste heat, flue-gas heat recovery, and processes described in our flue-gas cooling and white-plume article. Stainless shrugs off corrosion that would destroy aluminum in a season. The trade-off is weight and cost, and its lower conductivity means you need a larger surface area for the same duty — which is why stainless cores are usually welded plate designs, such as our high-temperature welded plate exchanger.
Aluminum — The HVAC Default
Aluminum is the workhorse for comfort HVAC: fresh-air handling units, HRV/ERV cores, and data-center free cooling. Its high conductivity lets a compact core hit 80–90% effectiveness, and it is light enough for rooftop units. For moist or condensing streams, a hydrophilic coating is applied so condensate sheets off instead of beading — the same coating behind our heat-pump drying foil core. Aluminum's limit is temperature and strong chemicals; above ~150°C or in acid exhaust, move to stainless or PP.
PP Polymer — The Chemical-Resistant Lightweight
Polypropylene plates solve the duty aluminum and steel cannot: highly corrosive, acidic, or erosive exhaust where metal would pit or foul. PP is inert, light, and cheap, and it resists the condensation and chemical attack common in plating, etching, and scrubber exhausts. Our dedicated piece on PP polymer heat exchangers covers the chemistry. The cost is temperature ceiling (around 70–80°C) and lower conductivity, so PP cores are larger for a given duty — acceptable when corrosion would otherwise end the unit's life in months.
How to Choose
- Temperature > 150°C or acidic/particulate exhaust → stainless steel.
- Comfort HVAC, fresh air, free cooling, ≤ 150°C, dry or coated → aluminum.
- Corrosive/chemical exhaust, ≤ 80°C → PP polymer.
- Confirm the core form (plate/rotary/heat-pipe) independently — see plate, rotary, heat-pipe.
Material and Selection Together
Material is only half the spec. Pair it with the right core and duty — our selection guide and efficiency reference close the loop. For a corrosion-duty quotation, contact +86 15753355505.