The one difference: carbon
SS316 and SS316L share the same chromium (16–18%), nickel (10–14%) and molybdenum (2–3%). The "L" stands for low carbon: SS316 allows up to 0.08% carbon, SS316L only up to 0.03%.
Why carbon matters: sensitisation
When austenitic stainless steel is held roughly between 425 °C and 870 °C — which happens in the heat-affected zone next to a weld — carbon combines with chromium to form chromium carbides at the grain boundaries. The metal right beside those boundaries loses chromium and with it the ability to stay passive. This is called sensitisation.
In a corrosive environment, a sensitised zone can suffer intergranular corrosion: attack that runs along grain boundaries, often invisible until the part cracks or leaks.
With carbon held at 0.03% or below, there is too little carbon to form damaging amounts of carbide during normal welding — so SS316L keeps its corrosion resistance in the weld zone without post-weld solution annealing.
What you give up with 316L
Carbon contributes to strength, so 316L has slightly lower minimum strength. Under ASTM A276 (annealed bar), typical minimums are:
| Property (min.) | SS316 | SS316L |
|---|---|---|
| Tensile strength | 515 MPa | 485 MPa |
| Yield strength (0.2%) | 205 MPa | 170 MPa |
| Max. carbon | 0.08% | 0.03% |
For most process equipment the difference is irrelevant; for highly stressed components, check your design margin.
Which one to buy
- Choose SS316L for welded fabrications in corrosive service — chemical and pharma vessels, piping supports, tanks, heavy weldments, and any part that can't be solution-annealed after welding.
- SS316 is fine for machined parts that are not welded — shafts, fasteners, valve components — and where the extra strength is useful.
- High-temperature service (continuous operation in the sensitisation range) needs an engineering review regardless of grade; low carbon alone is not a complete answer there.
What to check on the MTC
Look at the carbon value. For 316L it must read 0.030% or less. Also confirm molybdenum is at least 2.0% — a low Mo reading is the classic sign of 304 being sold as 316. Our guide on how to read an MTC walks through every line.
Navkardeep Steel melts SS316 and SS316L in-house with spectrometer-verified chemistry on every heat. See our SS316L and SS316 grade pages or ask for a quote.