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| Grade | Key Properties | Chloride Resistance | Recommended Applications |
| 304 | Most economical | Poor (≤200 ppm Cl⁻) | Nitric acid (<30%, ≤100°C), organic solvents. Avoid HCl/H₂SO₄. |
| 304L | Low carbon (≤0.03%) | Slightly better than 304 | Welded heat exchangers (PHEs), improved weld zone corrosion resistance. |
| 316 | 2% Mo addition | Moderate (≤1000 ppm Cl⁻) | Cooling water, seawater (limited), acetic acid. Avoid sulfuric acid. |
| 316L | Low carbon version | Better weld resistance | Same as 316, for welded structures. |
| Grade | Key Features | Chloride Resistance | Specialty Uses |
| 317 | Higher Cr/Mo/Ni | 1.5× better than 316 | High-chloride, high-temperature services. |
| 904L | 20% Cr, 25% Ni, 4.5% Mo | Excellent(≤5000 ppm Cl⁻) | Sulfuric/phosphoric acids, halides (Cl⁻/F⁻). |
| 254SMo | Super austenitic | Outstanding (≤15,000 ppm Cl⁻) | Brine, seawater, HCl alternatives. |
| (6% Mo) |
| Alloy | Composition | Chloride Performance | Limitations |
| Incoloy 825 | Ni(40%)-Cr(22%)-Mo(3%) | Good in H₂SO₄/NaOH | Poor crevice corrosion resistance. |
| 31 Alloy | Upgraded 904L | >904L in hot H₂SO₄ | Costly,but outperforms C-276 in some acids. |
| (6% Mo) | |||
| C-2000 | Ni-Cr-Mo (59% Ni) | Best-in-class | Replaces C-276 in ≤50% H₂SO₄/HCl. |
Quick Selection Criteria
Low Chloride (<200 ppm): 304/304L
Moderate Chloride (200-1000 ppm): 316/316L
High Chloride (1000-5000 ppm): 904L/317
Severe Chloride (>5000 ppm): 254SMo/Nickel alloys (C-2000/59)
Critical Notes
Temperature: Max service temp drops ~20°C for every 10× Cl⁻ increase.
Welding: Use "L" grades (304L/316L) for welded assemblies.
Cost-Performance Balance: 904L for most acidic chlorides; nickel alloys for extreme conditions.
Corrosion Resistance Hierarchy
Cl⁻ Resistance: 304 < 316L < 904L < 254SMo < Nickel Alloys
Cost: Nickel Alloys ≫ 254SMo > 904L > 316L > 304
