409 is a general purpose chromium, titanium stabilized ferritic stainless steel whose primary application is in automotive exhaust systems. It contains 11% chromium, the minimum amount to form a passive surface film that gives stainless steel its corrosion resistance. It combines good high temperature corrosion resistance with moderate strength, good formability, and overall cost. 409 has strong corrosion resistance compared to carbon steel and is used as a replacement for carbon steel in mildly challenging environments where its high resistance to corrosion and high temperature oxidation is an advantage. It is often used in applications where appearance is a secondary quality to mechanical properties and corrosion resistance.