The L in 316L austenitic stainless steel indicates a Lower Carbon Content. This is the most significant difference between Type 316L and the more common Type 316 stainless steel. A lower carbon content makes 316L softer than 316 stainless steel. This leads to a variety of differences in its machinability, weldability, and corrosion resistance.
316L stainless steel is a weld friendly grade of stainless steel. It can be welded to other steels or metals, and forms shapes more easily. While standard 316 stainless can be welded it is susceptible to weld decay, leading to corrosion in the weld and a weakening of the bond.
316L has slightly better corrosion resistance than the 316 grade, but 316 has a higher tensile strength and hardness than 316L. Fasteners are more commonly available in 316, but for applications that require welding 316L stainless steel is the preferred choice. Due to the fact that 316L and 316 stainless contain 2% Molybdenum (Mo) they are more corrosion resistant than 304 stainless steels, particularly in chloride environments.