"Should I take 304 or 316?" It is one of the most common questions in the stainless steel trade. The SS 304 vs SS 316 decision affects corrosion life, price and sometimes the safety of an entire plant. Buyers expect their supplier to answer it confidently. This guide explains the real differences, where each grade fits, and how to advise customers without overselling.
The short answer
- SS 304 is the general-purpose austenitic stainless steel. It resists corrosion well in most indoor, food and water applications.
- SS 316 adds molybdenum, which gives much better resistance to chlorides — salt water, coastal air, de-icing salts and many chemicals.
If chlorides are present, 316 is usually the safer choice. If they are not, 304 normally does the job at a lower cost.
Chemical composition compared
Typical limits per ASTM A240 / A312 (weight %):
| Element | SS 304 | SS 316 |
|---|---|---|
| Chromium (Cr) | 18.0 – 20.0 | 16.0 – 18.0 |
| Nickel (Ni) | 8.0 – 10.5 (A240) | 10.0 – 14.0 |
| Molybdenum (Mo) | — | 2.0 – 3.0 |
| Carbon (C) max | 0.08 | 0.08 |
| Manganese (Mn) max | 2.00 | 2.00 |
The extra nickel and molybdenum in 316 are also why it costs more — both are expensive alloying elements whose prices move with global markets.
Corrosion resistance
General corrosion
In clean water, indoor air, food processing and most architectural use, both grades perform well. 304 is often more than enough.
Pitting and crevice corrosion
Chlorides attack stainless steel by causing small pits, especially in crevices and under deposits. Molybdenum strongly improves resistance to this. A common comparison tool is the Pitting Resistance Equivalent Number (PREN):
PREN = %Cr + 3.3 × %Mo + 16 × %N
- SS 304: around 18–20
- SS 316: around 23–25
A higher PREN means better resistance to pitting. That is why 316 is the standard choice for marine, coastal and chemical environments.
Mechanical properties
Both grades have very similar strength in the annealed condition. ASTM A240 sets a minimum tensile strength of 515 MPa and a minimum yield strength of 205 MPa for both. Both are non-magnetic when annealed (cold working can make them slightly magnetic), both are easy to weld, and both perform well at low temperatures.
So the decision is almost never about strength. It is about the environment.
What about 304L and 316L?
The "L" stands for low carbon — a maximum of 0.030% instead of 0.08%. Low carbon reduces the risk of sensitisation, where chromium carbides form at grain boundaries during welding and leave the area open to corrosion.
- Choose L grades for heavily welded fabrications.
- Many mills supply dual-certified 304/304L and 316/316L material that meets both sets of requirements. Mention this on your product pages — buyers search for it.
Typical applications
SS 304
- Kitchen equipment and food processing
- Dairy and beverage plants
- Indoor architectural work and railings
- Water tanks and general plumbing
- Low-chloride process piping
SS 316 / 316L
- Marine hardware and coastal structures
- Chemical and pharmaceutical plants
- Desalination and seawater-adjacent lines
- Oil & gas instrumentation tubing and fittings
- Swimming pool equipment
- Medical and high-purity applications
Cost difference
The price gap between 304 and 316 is not fixed. It moves with nickel and molybdenum prices, and 316 has historically cost noticeably more per kilo. Always quote both grades from current prices rather than a rule of thumb. Our steel price calculator helps you work out price per piece or per metre including GST.
How to advise buyers
- Ask about the environment. Coastal? Chemicals? Chlorinated water? Cleaning agents? These answers decide the grade.
- Ask about welding. Heavy welding points toward 304L or 316L.
- Never substitute silently. Supplying 304 where 316 was ordered is a serious quality failure. Buyers can check molybdenum with a handheld PMI analyser in seconds.
- Back it with a correct MTC. The mill test certificate must show the exact grade, standard and chemistry. MTCMitra checks every value against the grade limits before you print.
Frequently asked questions
Is SS 316 magnetic?
In the annealed condition, both 304 and 316 are essentially non-magnetic. Cold working, bending or machining can make them slightly magnetic, so a magnet test alone cannot tell the grades apart.
How can a buyer check if material is 304 or 316?
A handheld PMI (positive material identification) analyser shows the molybdenum content in seconds. 316 contains about 2–3% molybdenum, while 304 has almost none.
Can I use 304 in coastal areas?
304 can show tea staining and pitting in salty coastal air. 316 is usually the better choice near the sea, especially for outdoor structures and fittings.
Are 316 and 316L interchangeable?
Dual-certified 316/316L meets both specifications. If the buyer orders 316L for welded service, single-certified 316 with higher carbon should not be supplied in its place.
Key takeaways
- 316 = 304 + molybdenum + more nickel → better chloride resistance.
- Strength is almost the same; the environment decides the grade.
- Use L grades for welded work; dual-certified material covers both.
- Quote both grades when the application is unclear, and explain why.
Suppliers who explain the difference clearly win the buyer's trust — and often the long-term contract that follows.
