304L grade with 0.030% maximum carbon is similar to the 304 grade, but with much enhanced performance in the sensitization range. Due to its superior resistance to intergranular corrosion following stress relieving or welding, Type 304L is broader in application versatility. The extra-low carbon 304L is required when welding joins heavy sections or an aggressive corrosion environment exists and post-weld annealing is not possible. 304L will become sensitized if exposed for long periods of exposure to service temperatures of 800°-1600°F.
Type 304L is used where welding is required but the carbide precipitation tendency of Type 304 will impair that alloys corrosion resistance.