When to choose 304L over 316L
304L lacks the 2–3% molybdenum of 316L, so its pitting resistance in chloride environments (sea water, brine, chlorinated process fluids) is materially lower. For end-uses where the filtered medium is not aggressive — compressed air, dry gases, mineral hydraulic oil, hot water, low-grade steam — 304L delivers equivalent mechanical strength after sintering at lower per-kilogram cost.
Many filter cartridge OEMs maintain parallel 316L and 304L product lines and pick by application; we supply both from the same atomization line so chemistry and morphology are consistent across the two.
Available cut points
| SKU | Cut point | Typical D50 | Typical use |
|---|---|---|---|
| 304L 150 mesh | ≈100 µm | 75–90 µm | Coarse support layer, single-layer 20–40 µm filtration |
| 304L 200 mesh | ≈75 µm | 55–65 µm | Single-layer 5–15 µm filtration, transition layer |
| 304L 250 mesh | ≈58 µm | 40–48 µm | Fine layer, 1–5 µm filtration, membrane substrate (cost-down) |
Chemistry (UNS S30403)
| Element | Range (wt%) | Typical |
|---|---|---|
| C | ≤ 0.030 | 0.020 |
| Cr | 18.0 – 20.0 | 18.6 |
| Ni | 8.0 – 12.0 | 10.0 |
| Mn | ≤ 2.0 | 1.5 |
| Si | ≤ 1.0 | 0.6 |
| P | ≤ 0.045 | 0.018 |
| S | ≤ 0.030 | 0.012 |
| N | ≤ 0.10 | 0.05 |
| Fe | Balance | — |
OES verification per batch.
Physical properties
Apparent density 2.6–2.9 g/cm³ across SKUs; tap density 3.4–3.8 g/cm³; oxygen ≤ 3000 ppm. The same QC envelope as our 316L line.
Application notes
- General-purpose compressed-air filtration: 304L 150 mesh + 250 mesh multi-layer is a high-volume SKU pair for shop-air dryers and instrument-air filters.
- Hot water and low-grade steam: 304L performs well as long as chloride concentration is controlled. For boiler blowdown, condensate, or sea-water adjacent applications, specify 316L instead.
- PM structural parts: 304L sinters to similar densities as 316L; pick by chemistry, not by sintering behavior.
When to upgrade to 316L
- Saline or brine-bearing media
- Pharmaceutical or food-grade processing where regulatory pressure favors 316L
- Polymer melt filtration above 250 °C
- Customer specifies UNS S31603 in the part drawing
We can ship a 316L equivalent of any 304L SKU on the same lead time.