What Makes SS316 Different from SS304?
The difference is one element: molybdenum.
SS304 contains approximately 18% chromium and 8–10.5% nickel. That is it — chromium and nickel are the two main alloying elements.
SS316 contains the same chromium and nickel, plus 2–3% molybdenum.
That small addition of molybdenum changes the corrosion behaviour of the steel significantly — specifically its resistance to chloride-induced pitting and crevice corrosion.
What Is Chloride Corrosion and Why Does It Matter?
Chloride ions are found in:
- Seawater and coastal air
- Swimming pool water
- Many cleaning chemicals (sodium hypochlorite, bleach)
- Food processing brines and marinades
- Chemical process streams
- Industrial cooling water
When chloride ions attack SS304, they penetrate the passive chromium oxide layer and cause pitting — small, deep holes that grow inward and eventually cause perforation or cracking. This process is called pitting corrosion and it happens even when the surface looks clean and shiny.
SS316's molybdenum content stabilises the passive layer against chloride attack. It does not make the steel immune to chlorides, but it dramatically raises the concentration and temperature at which pitting begins.
Chemical Composition Comparison
| Element | SS304 | SS316 |
|---|---|---|
| Chromium | 18–20% | 16–18% |
| Nickel | 8–10.5% | 10–14% |
| Molybdenum | None | 2–3% |
| Carbon (max) | 0.08% | 0.08% |
| Manganese (max) | 2% | 2% |
Mechanical Properties Comparison
| Property | SS304 | SS316 |
|---|---|---|
| Tensile Strength (min) | 515 MPa | 515 MPa |
| Yield Strength (min) | 205 MPa | 205 MPa |
| Elongation (min) | 40% | 40% |
Mechanically, they are essentially the same. The difference is entirely in corrosion behaviour.
When to Use SS304
SS304 is the right choice when:
- The environment does not contain significant chlorides
- Indoor application with no exposure to coastal air or chemical cleaning agents
- General engineering parts — shafts, brackets, machine components
- Food processing equipment where cleaning agents are mild (caustic soda, phosphoric acid)
- Architectural applications in non-coastal cities
- General fabrication where budget is a consideration
SS304 is the world's most widely used stainless steel grade. It handles most industrial environments, most food environments, and most architectural applications perfectly well at a lower cost than SS316.
When to Use SS316
SS316 is the right choice when:
- The application involves exposure to chlorides — seawater, coastal air, brine, bleach
- Chemical plant service with acids or process chemicals
- Pharmaceutical equipment that sees aggressive CIP chemicals
- Food processing with salt, vinegar, or meat (which contains blood — a chloride-containing fluid)
- Marine and offshore structures
- Swimming pool surrounds
- Any application where pitting or crevice corrosion has caused failures before
What About SS316L?
The "L" in SS316L stands for Low Carbon. The carbon content is held below 0.03% (compared to 0.08% maximum in standard SS316).
Use SS316L when the material will be welded. During welding, the heat-affected zone reaches temperatures where carbon migrates to grain boundaries and forms chromium carbides — a process called sensitisation that strips chromium from those zones and creates corrosion-vulnerable areas.
Low carbon (316L) prevents this. If your fabricator is welding the bars into an assembly, always specify 316L.
If the bars will only be machined (not welded), standard SS316 is fine.
Cost Consideration
SS316 costs approximately 15–25% more than SS304 at current prices, due to the molybdenum addition. For large projects, this cost difference is real money.
The right approach: use SS304 wherever the environment genuinely does not require SS316, and use SS316 only where the chloride or chemical exposure justifies it. Do not over-specify — but do not under-specify either.
Quick Decision Guide
| Your Application | Recommended Grade |
|---|---|
| Indoor machine parts, no chemical exposure | SS304 |
| Outdoor structure, non-coastal city | SS304 |
| Coastal area, within 5km of sea | SS316 |
| Chemical plant | SS316 |
| Pharmaceutical equipment (welded) | SS316L |
| Food processing, mild cleaning chemicals | SS304 |
| Meat processing, dairy, brine exposure | SS316 |
| Swimming pool area | SS316 |
| General fabrication, indoor use | SS202 or SS304 |
Still Not Sure?
Send us your application details on WhatsApp — our technical team will recommend the right grade at no charge. We would rather help you specify correctly than supply the wrong material.
Navkardeep Steel supplies SS304, SS316 and SS316L round bars, hex bars, flat bars, angles and channels from our plant in Vijapur, Mehsana, Gujarat. MTC with every order.