Stainless Steel 309S is classified as a highly alloyed stainless steel. It contains less nickel in its composition than Type 310 and a lower carbon amount than its Type 309 counterpart. The reduced nickel allows for better resistance against hydrogen sulfide, especially at high temperatures. Additionally, the lower amount of carbon in its composition gives Stainless Steel 309S utilization in areas where high temperature gases may pose a problem. As such, it is commonly applied in the manufacturing of furnaces, exhaust systems and containers exposed to high temperatures.
Type 309S is additionally characterized by its resistance to oxidation and creep, along with its ability to withstand high temperatures. Moist environments have no effect on it, due to the higher levels of nickel and chromium in its makeup. Because of this, it is often utilized in marine environments in place of Stainless Steel 304, as it displays a higher resistance. Despite its excellent weldability, Type 309S does have a tendency to work harden.
