AK Steel 439 is a ferritic stainless steel that outperforms Type 409 in both oxidation resistance and corrosion resistance. Special attention to chemical composition combined with special processing give this alloy optimum formability that is reproducible, coil after coil and heat after heat. This provides special advantages when producing difficult-to-form exhaust systems components.

Oxidation and corrosion resistance superior to Type 409 makes AK Steel 439 Stainless Steel attractive for numerous automotive exhaust applications. Typical uses include tubular manifolds and other exhaust system components where temperatures may exceed the oxidation limit of Type 409, or where wet corrosion resistance, particularly to chlorides, is needed.