Grade 304 and Grade 316 are the two most widely stocked austenitic stainless steel grades for pipe, fittings, and flanges. They look identical and share similar mechanical properties, but one chemistry difference — molybdenum — decides which one is right for a chloride-exposed or chemical-process application.
Chemical Composition Comparison
| Element | Grade 304 / 304L | Grade 316 / 316L |
|---|---|---|
| Chromium (Cr) | 18–20% | 16–18% |
| Nickel (Ni) | 8–10.5% | 10–14% |
| Molybdenum (Mo) | None | 2–3% |
| Carbon (C) | ≤0.08% (304), ≤0.03% (304L) | ≤0.08% (316), ≤0.03% (316L) |
| Manganese (Mn) | ≤2% | ≤2% |
The Key Difference: Molybdenum & Corrosion Resistance
Molybdenum is the deciding factor. 316’s 2–3% Mo content significantly improves resistance to pitting and crevice corrosion in chloride-rich environments — seawater, brine, and many process chemicals — where 304 is prone to localized attack. In general atmospheric, freshwater, and most food/dairy/pharma-grade applications, 304 performs just as well as 316 at a lower cost.
When to Specify Each Grade
- Grade 304/304L — suitable for: general process piping, food & beverage lines, dairy equipment, architectural/decorative work, most indoor industrial piping with no chloride exposure.
- Grade 316/316L — required for: marine and coastal installations, chemical and petrochemical process lines handling chlorides/acids, pharmaceutical and biotech piping (where spec often mandates 316L specifically), offshore and desalination equipment.
Mechanical Properties (Typical, Both Grades)
304 and 316 share near-identical mechanical properties as seamless pipe per ASTM A312: minimum tensile strength ≈515 MPa (75,000 psi), minimum yield strength ≈205 MPa (30,000 psi) for the standard (non-L) grades. The “L” (low-carbon) variants have marginally lower minimum tensile/yield but far better resistance to carbide precipitation during welding — the standard choice for any pipe that will be field-welded.
Figures shown are typical published composition/property ranges per ASTM A240/A312; always confirm against the current standard edition and the heat-specific Mill Test Certificate for critical or code-stamped work. Seamless Steel Industries stocks both 304/304L and 316/316L seamless & welded pipe — request a quotation specifying your exact service conditions if you’re unsure which grade fits.