Your choice between 304 and 316 stainless steel sets how long your part lasts and what you pay per tonne. This guide shows where the two grades really differ and which one fits your environment.
What Is the Main Difference Between 304 and 316 Stainless Steel?
The main difference is molybdenum. 316 contains 2–3% molybdenum and more nickel than 304. This gives 316 much better resistance to chlorides, salt and many acids. 304 has no added molybdenum, so it costs less and performs well indoors and in mild outdoor conditions.
Everything else follows from this one alloying change. The two grades look the same, weigh almost the same and are formed and welded the same way.
Chemical Composition of 304 and 316
The table below shows the limits for plate, sheet and strip under ASTM A240. Pipe & Tube and bar standards use slightly different ranges.
| Element (wt%) | 304 | 316 |
|---|---|---|
| Carbon (C) | ≤ 0.07 | ≤ 0.08 |
| Chromium (Cr) | 17.5–19.5 | 16.0–18.0 |
| Nickel (Ni) | 8.0–10.5 | 10.0–14.0 |
| Molybdenum (Mo) | — | 2.00–3.00 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 |
| Silicon (Si) | ≤ 0.75 | ≤ 0.75 |
| Nitrogen (N) | ≤ 0.10 | ≤ 0.10 |
You will also see these grades under other names:
| Standard | 304 | 316 |
|---|---|---|
| UNS | S30400 | S31600 |
| EN | 1.4301 | 1.4401 |
| JIS | SUS304 | SUS316 |
Note that 316 actually has slightly less chromium than 304. Its advantage comes from molybdenum, not from extra chromium.
Corrosion Resistance: Where 316 Earns Its Price
Both grades protect themselves with a thin chromium oxide layer. Chloride ions attack this layer at small weak points. The result is pitting and crevice corrosion, which can go deep while the surface still looks clean.
Molybdenum makes the passive layer far more stable against chlorides. Engineers compare this with the Pitting Resistance Equivalent Number (PREN = %Cr + 3.3 × %Mo + 16 × %N). 304 typically scores about 18–20. 316 typically scores about 23–26.
In practice, this means:
- Coastal air and sea spray: 316 resists tea staining and pitting far better than 304.
- De-icing salts: Road salt near bridges, car parks and entrances attacks 304 quickly.
- Food with salt or acids: Brine, sauces, pickles and dairy cleaning chemicals favor 316.
- Chemical and pharmaceutical plants: 316L is the usual starting grade.
Neither grade is a full answer for permanent seawater immersion or hot chloride solutions. In those cases, look at 2205 duplex instead. Our duplex stainless steel pipe & tube page covers that option.
One point many buyers miss: sheltered outdoor surfaces often corrode faster than exposed ones. Rain washes salt off open surfaces. Under canopies and inside channels, salt builds up and stays wet. If your part sits in a sheltered coastal spot, choose 316 even when the rest of the structure uses 304.
Mechanical Properties and Temperature
Strength is almost the same, so you rarely choose between these grades for strength. The figures below are ASTM A240 minimums for annealed material.
| Property | 304 | 316 |
|---|---|---|
| Tensile strength, min | 515 MPa | 515 MPa |
| Yield strength (0.2%), min | 205 MPa | 205 MPa |
| Elongation, min | 40% | 40% |
| Hardness, max | 201 HBW | 217 HBW |
| Density | 7.93 g/cm³ | 7.98 g/cm³ |
316 is about 1% heavier for the same size. This matters when you calculate sheet or coil weight for a large order.
At elevated temperatures, 316 keeps its strength slightly better because of molybdenum. Both grades stay tough at cryogenic temperatures. For continuous service in very hot furnace parts, heat-resistant grades such as 309S and 310S are a better fit. See our 310 stainless steel pipe & tube for that range.
Both grades are non-magnetic when annealed. Cold work such as bending, rolling or deep drawing can make either one slightly magnetic. So a magnet cannot tell you whether you have 304 or 316. The mill test certificate (MTC) can, because it lists the molybdenum content.
Fabrication and Welding
304 and 316 bend, draw and weld in very similar ways. You can use the same tooling and the same weld procedures, with one change in filler metal.
Use these fillers:
- 304 to 304: ER308L
- 316 to 316: ER316L
- 304 to 316: ER316L, so the joint keeps its molybdenum
Do not weld 316 with 308L filler. The weld then contains no molybdenum and becomes the weak point in a chloride environment.
Carbon content matters for thicker welded parts. Standard grades can form chromium carbides in the heat-affected zone during welding. This is called sensitization, and it leads to intergranular corrosion. Low-carbon 304L and 316L (C ≤ 0.030%) avoid this problem. Choose L grades for welded sections over about 6 mm, and for any welded part in corrosive service.
Dual-certified 304/304L and 316/316L is widely available. It meets the low-carbon limit and the strength of the standard grade. It is usually the simplest choice for welded fabrications.
If your parts need heavy machining, neither grade is ideal. Both are tough and tend to work-harden at the tool. Free-machining 303 stainless steel rod cuts much faster, as long as you do not need to weld it.
Cost: Why 316 Costs More
316 contains more nickel and adds molybdenum. Both are expensive alloying elements. So 316 always costs more than 304 in the same form and size.
The gap is not fixed. It moves with nickel and molybdenum market prices, so check it when you request a quote.
The better question is total cost over the life of the part. A 304 handrail that pits near the coast needs cleaning, repair or early replacement. That usually costs far more than the upgrade to 316. On the other hand, specifying 316 for dry indoor equipment adds cost and gives you no real benefit.
304 or 316? Choose by Environment
Use this table as a starting point. Your project specification or the end user’s standard always comes first.
| Environment or application | Grade to start with | Reason |
|---|---|---|
| Indoor equipment, appliances, dry interiors | 304 | No chloride exposure; lower cost |
| Kitchen and catering equipment | 304 | Good resistance to food and regular cleaning |
| Inland outdoor architecture, cleaned regularly | 304 | Rain washing and low salt levels |
| Coastal buildings, marine fittings, sea spray | 316 | Chloride resistance from molybdenum |
| Areas exposed to de-icing salts | 316 | Salt attack on 304 surfaces |
| Food processing with brine, sauces or acids | 316 / 316L | Pitting resistance in salty, acidic media |
| Chemical, pharmaceutical and medical equipment | 316L | Corrosion resistance plus good weldability |
| Heavy welded structures in corrosive service | 304L or 316L | Avoids sensitization at the welds |
Before you place an order, answer three questions:
- Will the steel touch chlorides? Think about salt air, de-icing salts, process fluids and cleaning chemicals.
- Will it be welded, and how thick is it? Thicker welded sections need an L grade.
- Will rain or cleaning keep the surface clean? Sheltered, dirty surfaces need a higher grade.
If any answer points to chlorides or poor cleaning, choose 316. If all three point to a dry, clean environment, 304 is the sensible choice.
Available Forms of 304 and 316 Stainless Steel
Both grades come in every common product form. Choose the form first, then the grade.
| Product form | 304 | 316 |
|---|---|---|
| Sheet (under 3 mm) | 304 stainless steel sheet | 316 stainless steel sheet |
| Plate (3 mm and above) | 304 stainless steel plate | 316 stainless steel plate |
| Coil | 304 stainless steel coil | 316 stainless steel coil |
| Pipe & Tube | 304 stainless steel pipe & tube | 316 stainless steel pipe & tube |
| Round bar | 304 stainless steel rod | SS 316 rod |
Both grades also come in common surface finishes, from 2B and BA to No.4, hairline and 8K mirror.
FAQ
Is 316 Stainless Steel Better Than 304?
316 is better in chloride and acidic environments because it contains 2–3% molybdenum. In dry indoor conditions, both grades perform the same, and 304 costs less. So “better” depends on where the part will be used, not on the grade number. Choose 316 for salt, chlorides and harsh cleaning chemicals. Choose 304 for clean, dry service where budget matters.
Can 304 Stainless Steel Be Used Outdoors?
Yes. 304 performs well outdoors in inland areas with low pollution, especially where rain washes the surface clean. It is widely used for railings, facades and equipment away from the coast. Near the sea, close to de-icing salts or in heavy industrial air, choose 316 instead. Regular cleaning also extends the life of 304 outdoors.
Is 316 Stainless Steel Magnetic?
No. Annealed 316 is non-magnetic, just like annealed 304, because both are austenitic grades. Cold forming such as bending, rolling or deep drawing can make either grade slightly magnetic in the worked areas. This does not reduce corrosion resistance. It does mean a magnet cannot separate 304 from 316, so rely on the mill test certificate instead.
What Is the Difference Between 316 and 316L?
316L has a maximum carbon content of 0.030%, compared with 0.08% for 316. Lower carbon prevents chromium carbides from forming during welding. This protects the heat-affected zone from intergranular corrosion. Choose 316L for welded parts, especially sections thicker than about 6 mm. Dual-certified 316/316L meets both specifications, so one material covers both requirements.
Can You Weld 304 to 316?
Yes. 304 and 316 weld together easily with standard TIG or MIG processes. Use ER316L filler so the weld metal keeps its molybdenum. The joint will then resist corrosion at least as well as the 304 side. Avoid ER308L filler in chloride service, because the weld would contain no molybdenum and corrode first.
How Can I Confirm I Received 316 and Not 304?
Check the chemical analysis on the mill test certificate supplied with the material. 316 must show molybdenum between 2.00% and 3.00%, and nickel between 10.0% and 14.0%. 304 shows no specified molybdenum and nickel between 8.0% and 10.5%. Also make sure the certificate states the grade and standard you ordered, such as ASTM A240 316.
Is 304 or 316 Food Grade?
Both grades are widely used for food contact surfaces. 304 is the standard choice for most kitchen, catering and food processing equipment. 316 is preferred where food contains salt or acids, such as brine, sauces and dairy. It also suits plants that use strong chloride-based cleaning chemicals. Your local food-contact regulations decide the final requirement.
Conclusion
If your part stays dry or indoors, 304 gives reliable performance at a lower cost. If it meets salt, chlorides or harsh chemicals, 316 pays for itself. We process and stock both grades in Wuxi and cut them to your size. Send us your drawing for a quote.