SUS316L Stainless Steel: Low-Carbon 316 for Superior Corrosion Resistance

SUS316L is the Japanese Industrial Standard designation for a low-carbon variant of 316 stainless steel, equivalent to UNS S31603 and EN 1.4404 (X2CrNiMo17-12-2). The reduced carbon content distinguishes it from SUS316 (UNS S31600): with 0.030% carbon max, the grade does not form continuous chromium carbide networks at grain boundaries during welding, so the corrosion resistance of the weld heat-affected zone is retained without post-weld solution annealing.

Standard coverage and grade equivalents

SUS316L is specified in JIS G4303 (stainless steel bars) and JIS G4304 (hot-rolled stainless steel plate, sheet and strip); related product forms are covered by JIS G4305, JIS G3459 (pipes) and JIS G3463 (boiler and heat exchanger tubes).

Standard	Grade designation
JIS G4303 / G4304	SUS316L
ASTM A240 / A276	316L / UNS S31603
EN 10088	X2CrNiMo17-12-2 / 1.4404
GB	022Cr17Ni12Mo2

Chemical composition (JIS G4304, wt%)

Element	Requirement
Carbon	0.030 max
Silicon	1.00 max
Manganese	2.00 max
Phosphorus	0.045 max
Sulfur	0.030 max
Chromium	16.00 - 18.00
Nickel	12.00 - 15.00
Molybdenum	2.00 - 3.00

Mechanical properties

Typical guaranteed minimum mechanical properties for SUS316L plate in the solution-annealed condition per JIS G4304 are listed below. Values for thicker sections, bars and cold-rolled sheet may differ slightly from the table; always verify against the product standard of the specific mill certificate.

Property	Minimum value
Tensile strength	480 MPa
0.2% proof strength	175 MPa
Elongation	40%

Corrosion resistance

The combination of 16.00-18.00% chromium, 12.00-15.00% nickel and 2.00-3.00% molybdenum gives SUS316L distinctly better resistance to pitting and crevice corrosion than SUS304 in chloride-bearing environments, while the low carbon content protects the welded joints from sensitization. It performs well in dilute sulfuric and phosphoric acids, organic acids and marine atmospheres, although it is not immune to chloride stress corrosion cracking or attack in hot concentrated chloride solutions.

Typical applications

SUS316L is used for welded chemical and pharmaceutical process equipment, storage tanks, heat exchangers, food and beverage processing lines, desalination plant components, coastal architectural cladding and medical device housings where the low-carbon grade guarantees weld integrity without additional heat treatment.

Frequently asked questions

Q1: What is the difference between SUS316 and SUS316L? A1: The carbon content. SUS316 allows 0.08% carbon max, while SUS316L limits carbon to 0.030% max, which prevents sensitization and intergranular corrosion after welding.

Q2: Is SUS316L the same as EN 1.4404? A2: Yes, EN 1.4404 (X2CrNiMo17-12-2) is the European designation of the same low-carbon 17-12-2 molybdenum grade.

Q3: Does SUS316L require post-weld heat treatment? A3: No. The low carbon content is the standard solution for welded construction; post-weld solution annealing is generally not required for corrosion resistance.

Q4: Can SUS316L be used in seawater? A4: It is used in marine environments and has good resistance to general corrosion and pitting in ambient seawater, but for permanent immersion or warm seawater service, higher alloyed grades should be evaluated.

Q5: What is the maximum service temperature? A5: For continuous service, SUS316L is typically used up to about 400-450 degree C; above this range the low-carbon grade has lower creep strength than the standard-carbon 316 grade.