SS 304 or SS 316: choosing without overspending
316 costs meaningfully more than 304 and is specified far more often than it is needed — and occasionally not specified when it is essential.
4 min read · updated 30 October 2026
Both are austenitic stainless steels, both are non-magnetic, and both look identical. The difference is molybdenum: 316 contains roughly 2–3%, and 304 contains none.
What molybdenum does
Stainless resists corrosion through a passive chromium oxide film. Chloride ions attack that film locally, producing pitting — small, deep perforations that spread under deposits and in crevices. Molybdenum substantially improves resistance to exactly that mechanism. It does little for general corrosion, which is why 316 is not simply a better 304.
| SS 304 | SS 316 | |
|---|---|---|
| Density | 7,930 kg/m³ | 8,000 kg/m³ |
| Molybdenum | None | 2–3% |
| Chloride pitting resistance | Moderate | Good |
| Relative cost | Baseline | Noticeably higher |
| Magnetic | No (annealed) | No (annealed) |
When 304 is sufficient
- Interior architectural work — screens, ceilings, partitions.
- Clean hydrocarbon service at moderate temperature.
- Food processing with normal washdown, away from salt.
- General filtration where the stream is not chloride-bearing.
- Dry or sheltered exterior applications inland.
When 316 is worth the money
- Any permanently wet coastal exposure — which in Mumbai means most exterior stainless.
- Chloride-bearing process streams, including amine and glycol service.
- Pharmaceutical equipment, where it is effectively the default.
- Marine and offshore, though genuine seawater usually needs Monel rather than 316.
- Anywhere deposits can form and sit against the surface.
The L grades
304L and 316L have lower carbon content. During welding, carbon migrates to grain boundaries and combines with chromium, leaving those boundaries depleted and vulnerable — sensitisation. The L grades substantially reduce it.
The practical rule: if the part will be welded or fabricated — a basket, a rolled cylinder, a framed screen — specify the L grade. For flat sheet that will simply be cut and fixed, standard grade is fine.
A note on perforated sheet specifically
Perforation multiplies exposed surface area and creates a very large number of cut edges, each a potential initiation site. That makes grade selection matter more for perforated sheet than for the same alloy in solid plate — a point worth remembering when a specification is being value-engineered.
Common questions
- Can I tell 304 and 316 apart visually?
- No. They are visually identical, and both are non-magnetic when annealed. A molybdenum spot test or a portable XRF analyser will distinguish them — which is why material test certificates are worth asking for on anything critical.
- How much more does 316 cost?
- Noticeably more, and the premium moves with nickel and molybdenum prices rather than staying fixed. Ask for current rates on both when you enquire; on a large order the difference is worth a deliberate decision rather than a default.
- Is 316 stronger than 304?
- Not meaningfully. Their mechanical properties are close, and 316 is chosen for corrosion resistance rather than strength. If strength is the governing requirement, duplex grades are the better conversation.