316 (1.4401) vs. 316L (1.4404): Standard vs. Weld-Friendly Low-Carbon Stainless Steel

316 (1.4401) - Standard Grade

Carbon: Higher (max ~0.07-0.08%).

Best For: General corrosive environments where welding isn't heavy or post-weld annealing is done.

Weakness: More susceptible to intergranular corrosion (sensitization) after welding due to chromium carbides forming at grain boundaries.

316L (1.4404) - Low-Carbon Grade

Carbon: Lower (max ~0.03%).

Best For: Heavy gauge welded components, critical welded structures, pharmaceutical, chemical, and marine applications where corrosion resistance after welding is crucial.

Strength: Highly resistant to sensitization, making it weld-friendly without requiring post-weld heat treatment.

Key Similarities

Both contain Molybdenum (Mo), giving excellent resistance to pitting and crevice corrosion, especially in chloride/marine environments.

Both are austenitic, non-magnetic (when annealed), tough, and offer good high-temperature performance.