304 vs 316 Stainless Steel Pipe

304 (UNS S30400) and 316 (UNS S31600) are the two most widely used austenitic stainless steel grades for pipe. Both offer excellent general corrosion resistance. The defining difference is molybdenum: 316 contains 2-3% Mo, which gives it significantly better resistance to pitting, crevice corrosion, and chloride attack.

304 is the default when general corrosion resistance is adequate. 316 is the upgrade when chlorides, marine environments, or aggressive chemicals are present.

Comparison Table

Property	304/304L	316/316L
UNS number	S30400/S30403	S31600/S31603
Chromium	18-20%	16-18%
Nickel	8-11%	10-14%
Molybdenum	None	2-3%
Carbon (L grade)	0.035% max	0.035% max
Yield strength	170 MPa (25 ksi)	170 MPa (25 ksi)
Tensile strength	485 MPa (70 ksi)	485 MPa (70 ksi)
Pitting resistance (PREN)	~18-20	~24-28
Chloride resistance	Moderate	Good
Marine environment	Not recommended	Suitable
Max. service temp	~870°C (continuous)	~870°C (continuous)
Min. service temp	-196°C	-196°C
Cost	Base	+15-25%
Pipe spec	ASTM A312 TP304/304L	ASTM A312 TP316/316L
Fitting spec	ASTM A403 WP304/304L	ASTM A403 WP316/316L
Flange spec	ASTM A182 F304/304L	ASTM A182 F316/316L

When to Use 304

• General chemical processing where chlorides are absent or minimal
• Food and beverage production (FDA compliant)
• Pharmaceutical water systems (WFI, PW)
• Architectural and structural applications
• Cryogenic piping (both 304 and 316 are suitable)
• Freshwater systems

When 316 Is Required

• Chloride-containing environments (seawater cooling, brine, produced water)
• Marine and coastal installations
• Chemical processing with sulfuric acid, formic acid, or acetic acid
• Pharmaceutical process piping (some standards mandate 316L)
• Pulp and paper industry
• Desalination plants
• Offshore platforms and subsea equipment

Common Mistake

Specifying 304 for systems handling chloride-bearing fluids above 60°C. This invites stress corrosion cracking (SCC). At chloride concentrations above 25 ppm and temperatures above 60°C, 316 is the minimum grade. For higher chloride concentrations, consider duplex stainless steel or nickel alloys.

The “L” Grades

Both 304 and 316 come in low-carbon variants (304L and 316L) with carbon limited to 0.035% max (vs. 0.08% for standard grades). Low-carbon grades resist sensitization during welding, preventing intergranular corrosion in the heat-affected zone.

Most modern mills produce dual-certified material (meeting both standard and L-grade requirements), making the L grade the default for welded construction. There is no cost penalty for dual certification.

For environments beyond 316’s capability, duplex (ASTM A790) or nickel alloy pipes are the next step.

Read the full guide to pipe types