Choosing the grade is choosing the failure mode you are prepared to live with. Austenitic stainless handles a very wide range of media, but it has specific, well-understood vulnerabilities — and knowing where they are is more useful than a claim that it resists everything.
Rating scale
| Rating | Meaning |
|---|---|
| A | Suitable |
| C | Conditional — depends on concentration and temperature. Ask us. |
| X | Not recommended. Use a PTFE-lined hose or a special alloy. |
Common media
| Medium | SS 304L | SS 316L | Notes |
|---|---|---|---|
| Water — fresh, DM, condensate | A | A | |
| Steam, saturated or superheated | A | A | Apply the derating table |
| Seawater, brine, chlorides | X | C | Pitting risk — 904L, super duplex or PTFE-lined preferred |
| Nitrogen, argon, helium | A | A | |
| Compressed air | A | A | |
| Natural gas, CNG | A | A | |
| LPG | A | A | |
| Hydrogen | C | A | 316L preferred; consult us for high-pressure hydrogen |
| Oxygen | C | C | O₂-clean preparation mandatory; velocity limits apply |
| Ammonia, anhydrous | A | A | |
| Carbon dioxide, dry | A | A | Wet CO₂ becomes carbonic acid → C |
| Diesel, fuel oils, lube oil | A | A | |
| Ethanol, methanol | A | A | |
| Acetone, ketones | A | A | |
| Toluene, xylene, aromatics | A | A | |
| Caustic soda, dilute, ambient | A | A | Hot or concentrated → C |
| Nitric acid, dilute | A | A | Fuming or hot → C |
| Phosphoric acid | C | C | Dilute and cold acceptable in 316L; hot → 904L |
| Sulphuric acid | X | C | Only very dilute and cold; otherwise 904L or PTFE-lined |
| Hydrochloric acid | X | X | PTFE-lined only |
| Chlorine, dry gas | C | C | Wet chlorine → X, PTFE-lined |
| Milk, dairy, beverage | A | A | Sanitary tri-clamp, crevice-free welds |
| Vegetable oils, syrups | A | A |
The three mechanisms that actually cause trouble
Chloride stress corrosion cracking
The single most common cause of unexpected austenitic stainless failure. It needs three things together: chlorides, tensile stress and temperature above roughly 60 °C. A corrugated hose has residual forming stress built into it by definition, so two of the three conditions are already present in the product. Where chlorides are in the medium — or in the insulation, or in the coastal atmosphere outside the hose — the risk has to be assessed rather than assumed away.
Pitting and crevice corrosion
Localised breakdown of the passive layer, usually chloride-driven, and much worse in stagnant conditions than in flowing ones. It is why a hose that sat full of seawater over a shutdown can fail in weeks when the same hose in continuous service ran for years. 316L, with its molybdenum, resists it considerably better than 304L.
Intergranular attack
Chromium carbide precipitation at grain boundaries after sustained exposure in the 450–850 °C range, leaving the boundaries chromium-depleted and vulnerable. The low carbon grades (304L, 316L) and the stabilised grades (321) exist to control it. This is the reason we ask before publishing a pressure for 316L above 450 °C.