Stainless Steel in HVAC Systems: 304 vs. 316L

 

 

Why is 304 common for ductwork?
304 balances cost and atmospheric corrosion resistance for indoor air handling. Its smooth surface minimizes airflow resistance and microbial growth. Welded seams maintain integrity under static pressure up to 3,000 Pa.

 

When should HVAC use 316L?
Coastal or pool-adjacent installations demand 316L for salt-air resistance. Molybdenum prevents chloride-induced pitting in condenser coils and drain pans. Low carbon content avoids weld decay in brazed components.

 

How does condensation affect material choice?
Acidic condensate (pH 2.5-5) attacks unprotected steel. 316L withstands condensate corrosion 3x longer than 304. Sloped drain pans and copper-free brazing alloys further prevent galvanic corrosion.

 

What thickness suits HVAC components?
Sheet metal: 0.8-1.2mm for ducts, 1.5mm for structural supports. Coil tubing: 0.5mm wall thickness. Thicker gauges reduce vibration noise but increase system weight.

 

How to prevent galvanic corrosion?
Isolate stainless from copper/aluminum with dielectric unions. Avoid mixed-metal fasteners – use 316L screws with 316L brackets. Apply insulating tape between dissimilar metals in contact zones.