The main difference between 304 & 316 stainless steel:
304 does not contain molybdenum
316 contains 2-3% molybdenum and less chromium and more nickel.
The additional molybdenum:
providing pitting resistance in phosphoric acid, acetic acid and dilute chloride solutions
providing corrosion resistance in sulfurous acid.
AISI 304 has a 18% Cr and 8% Ni and therefore known as 18/8 stainless steel, while AISI 316 stainless steel has a 16% Chromium and 10% Nickel.
SS304 vs SS316 Difference in Chemical Composition (%)
| Element | Carbon (C) | Manganese (Mn) | Silicon (Si) | Phosphorus (P) | Sulfur (S) | Nitrogen (N) | Chromium (Cr) | Nickel (Ni) | Molybdenum (Mo) |
| 304 | ≤0.08 | ≤2.0 | ≤1.0 | ≤0.045 | ≤0.03 | ≤0.1 | 18.0-20.0 | 8.0-11.0 | NA |
| 316 | ≤0.08 | ≤2.0 | ≤1.0 | ≤0.045 | ≤0.03 | ≤0.1 | 16.0-18.0 | 10.0-14.0 | 2.0-3.0 |
SS304 vs SS316 Difference in Mechanical Properties
| Tensile Strength (Ultimate) Mpa | Tensile Strength (Yield) Mpa | Elongation A50 mm (2″) | Hardness (Brinell) | Hardness (Rockwell B) | |
| UTS N/mm | Yield N/mm | HBW | HRBW | ||
| 304 | ≥515 Mpa [75] | ≥205 Mpa [30] | ≥40% | ≤201 | ≤92 |
| 316 | ≥515 Mpa [75] | ≥205 Mpa [30] | ≥40% | ≤217 | ≤95 |
SS304 vs SS316 Difference in Physical Properties
| Density | Melting Point | Thermal Conductivity | Thermal Conductivity | Thermal Expansion | Thermal Expansion | |
| kg/dm3 (20℃/68℉) | ℃/℉ | 100℃/212℉ | 500℃/932℉ | 0-100℃/212℉ | 0-500℃/932℉ | |
| 304 | 7.93 | 1398-1454 ℃ 2548-2649℉ | 16.2 W/m.K | 21.5 W/m.K | 17.2 10^-6/K | 18.4 10^-6/K |
| 316 | 8 | 1370-1397 ℃ 2498-2546 ℉ | 16.3 W/m.K | 21.5 W/m.K | 15.9 10^-6/K | 18.5 10^-6/K |
| Electrical Resistivity | Modulus of Elasticity | Heat Resistance | |
| Ω . m2/m 20℃/68℉ | kN/mm2 20℃/68℉ | ||
| 304 | 0.73 | 193 GPa | continuous use at 425-860 °C (797-1580 °F) may cause corrosion. |
| 316 | 0.74 | 193 GPa | performs best above 843 ℃ (1550 ℉) and below 454 ℃ (850°F) |
SS304 vs SS316 Difference in Application & Cost
| 304 SS Application: |
| Food preparation: Fryers, food prep tables |
| Kitchen equipment: outdoor kitchen cabinet, cookware, kitchen sink |
| Architectural: siding, elevators, bathroom stalls, shower room/enclosure |
| Medical: medical cabinet, carts, trays |
| Cost: middle, practical and economical, affordable |
| 316 SS |
| Water-handling: boilers, water heaters |
| Marine environment & Coastal area: boat rails, wire rope, boat ladders |
| Chemical processing equipment |
| Medical equipment: surgical tools |
| Others: watch, clock, etc |
| Cost: around 40-50% higher than 304 |
| Corrosion: more resistant than 304 due to additional 2-3% molybdenum |
