Alloy 409 is a general purpose, chromium, titanium stabilized, ferritic stainless steel whose primary application is automotive exhaust systems. It contains 11% chromium which is the minimum amount for the formation of the passive surface film which gives stainless steels their corrosion resistance. It combines good elevated temperature corrosion resistance with medium strength, good formability, and overall cost. Alloy 409 resists corrosion strongly compared to carbon steel and is used as an alternative to carbon steel in mildly challenging environments where its high resistance to corrosion and high temperature oxidation gives an advantage. It is commonly used in applications where appearance is a secondary quality to mechanical properties and corrosion resistance.

Alloy 410 is the basic, general purpose martensitic stainless steel that is used for highly stressed parts and provides good corrosion resistance plus high strength and hardness. Alloy 410 contains a minimum of 11.5% chromium which is just sufficient enough to demonstrate corrosion resistance properties in mild atmospheres, steam, and many mild chemical environments. It is a general purpose grade that is often supplied in the hardened but still machineable condition for applications where high strength and moderate heat and corrosion resistance are required. Alloy 410 displays maximum corrosion resistance when it’s been hardened, tempered, and then polished.

Grade 430 is a ferritic, straight chromium, non-hardenable grade, combining good corrosion resistance and formability characteristics with useful mechanical properties. Its ability to resist nitric acid attack permits its use in specific chemical applications but automotive trim and appliance components represents its largest fields of application.