409 is a general purpose chromium, titanium stabilized ferritic stainless steel, its main application is automotive exhaust systems. It contains 11% chromium, which is the lowest amount to form a passive surface film, which makes stainless steel corrosion resistant. It combines good high temperature corrosion resistance, medium strength, good formability and overall cost. Compared with carbon steel, 409 has strong corrosion resistance and is used as a substitute for carbon steel in mildly challenging environments. In this environment, its high resistance to corrosion and high temperature oxidation has advantages. It is usually used in applications where appearance is a secondary quality to mechanical properties and corrosion resistance.