Why is 409 Stainless Steel the best choice for Outdoor Furnaces?

There is a lot of debate in the outdoor furnace industry about which steel is better to use.

We have made our choice based on the value that is provided to you, which is corrosion resistance, ability to withstand high temperatures, thermal expansion, heat transfer and cost effectiveness. Titanium Enhanced 409 Stainless Steel is our choice for good reason.

Heat Tolerance is what really sets 409 Stainless Steel apart from other steels in outdoor furnaces. It far outperforms all others steels and gives the furnace a long life. 409 Stainless Steel can withstand continuous temperatures of up to 1400º F while no other steel used in outdoor furnaces can withstand anything over 800ºF. This means that when the fire is over 800ºF mild steel will begin to oxidize and break down causing material failure which means a shorter life span.

Value Chart for Steels used in Outdoor Furnaces

Mild Steel 409 SS 304 SS
Corrosion Resistance No Yes Yes
Heat Transfer Good Good Not Good
Thermal Expansion Low Low High
Continuous Temperature Tolerance 600-800° 1400° 800°
Cost Good Good High


Corrosion Resistance

Stainless Steel is stainless because it has a chromium oxide film added to the steel. This film keeps oxygen from penetrating and corroding the material (rusting) and it’s why you see mild steel rusting while sitting out in the open. Mild steel will begin corroding from the first day of use and this is why many mild steel furnaces are at least 1/4” thick (to try to give the more life span).

Heat Transfer

409 Stainless Steel has the best heat transfer capability of any stainless steel used in outdoor furnaces, having about 60% more heat transfer capability than 304 SS and a similar heat transfer capability to mild steel when factoring in the thickness of material necessary for mild steel furnaces.

Thermal Expansion/Warping

409 Stainless Steel outperforms all other stainless steels used in outdoor furnaces. It has a low expansion rate and consequently won’t warp or get spider cracks.