316L Stainless Steel VS.18-8 Stainless Steel: Chemical Composition

316L Stainless Steel vs. 18-8 Stainless Steel: Chemical Composition and Performance Comparison

316L Stainless Steel

316L is an austenitic stainless steel and a low-carbon variant of 316 (the "L" stands for "Low Carbon"). It conforms to standards such as ASTM A240 and JIS G4303. The addition of molybdenum (Mo) gives it superior corrosion resistance compared to 304 stainless steel, especially in chloride-rich and humid environments.

18-8 Stainless Steel

"18-8" is a general classification rather than a specific grade, referring to austenitic stainless steels with approximately 18% chromium (Cr) and 8% nickel (Ni). The most common representative is 304 stainless steel (e.g., SUS304, ASTM 304). It is widely used due to its well-balanced mechanical and corrosion-resistant properties.

 

2. 316L Stainless Steel vs. 18-8 Stainless Steel: Chemical Composition Comparison (Typical Values)

Element	316L Stainless Steel (%)	18-8 Stainless Steel (304) (%)
Carbon (C)	≤ 0.03 (low carbon)	≤ 0.08 (standard carbon)
Chromium (Cr)	16.0–18.0	18.0–20.0
Nickel (Ni)	10.0–14.0	8.0–10.5
Molybdenum (Mo)	2.0–3.0	-
Other Elements	Mn, Si, P, S (trace amounts)	Same as 316L

---

 

3. 316L Stainless Steel vs. 18-8 Stainless Steel: Key Performance Differences

Corrosion Resistance

316L: Outstanding resistance to aggressive media like chlorides (e.g., NaCl), sulfuric acid, and phosphoric acid. Widely used in marine engineering, chemical processing, medical equipment, and desalination systems.

18-8 / 304: Good resistance in atmospheric, water, and steam environments. Suitable for kitchenware, architectural applications, and general piping, but vulnerable to pitting in saline or acidic environments.

Intergranular Corrosion

316L's ≤0.03% carbon makes it much less prone to chromium carbide precipitation in heat-affected zones (HAZ), thus more resistant to intergranular corrosion during welding-ideal for pressure vessels, welded piping, etc.

Mechanical Properties

Both are austenitic and exhibit similar room-temperature mechanical strength (Yield ≥205 MPa, Tensile ≥520 MPa).

316L offers better high-temperature strength and creep resistance, making it more suitable for continuous operation above 450°C.

Cost and Fabrication

316L is about 20–30% more expensive than 304 due to the Mo and higher Ni content.

Both offer excellent formability and machinability, though 316L tends to work-harden more during fabrication, requiring more robust tooling.

 

4.316L Stainless Steel vs. 18-8 Stainless Steel: Application Comparison

Application	316L Stainless Steel	18-8 / 304 Stainless Steel
Marine Environment	Heat exchangers, marine fasteners, offshore platform bolts	Coastal facades, non-critical marine components
Chemical Industry	Acid/alkali tanks, reactors, pharmaceutical equipment	General chemical piping and storage in mild environments
Food & Medical	Surgical instruments, hygienic-grade fermentation tanks	Food processing equipment, kitchen sinks
Architecture & Decor	Coastal curtain walls, ceilings in humid spaces	Interior design, railings in dry climates