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304 and 316 are the two most common austenitic stainless steel grades in UK engineering. 304 vs 316 Stainless Steel: Key Differences (UK Reference) Both give good general corrosion resistance, weldability, and formability. The headline difference: 316 contains 2% molybdenum, giving it far better resistance to chloride-induced pitting and crevice corrosion. 304 costs 30-50% less and handles most non-chloride environments.
304 vs 316 comparison table
| Property | 304 (1.4301) | 316 (1.4401) |
|---|
| Chromium | 18% | 17% |
| Nickel | 8% | 12% |
| Molybdenum | none | 2% |
| Tensile strength | 520 MPa | 520 MPa |
| Yield strength | 215 MPa | 215 MPa |
| Max service temp | 870C (continuous) | 870C (continuous) |
| Chloride resistance | poor | good |
| Typical price ratio | 1.0x | 1.3-1.5x |
| Magnetic? | slightly (cold worked) | slightly (cold worked) |
| Welding | excellent (304L for thick sections) | excellent (316L for thick sections) |
When to use 304
304 is the default stainless steel for general engineering, architectural trim, food processing equipment (where chloride exposure is limited), kitchen sinks, and fasteners (grade A2 is a 304 equivalent). It handles atmospheric corrosion, humidity, and most organic acids. If there's no seawater, road salt, pool chlorination, or bleach exposure, 304 is almost always the right call.
When to use 316
Specify 316 for marine hardware, pharmaceutical process equipment, coastal buildings, swimming pool handrails, brewing vessels, chemical pipework carrying chlorides, and any exterior component exposed to de-icing salt. Fastener grade A4 is a 316 equivalent. The 2% molybdenum content stops chloride ions from breaking through the passive chromium oxide layer, which is exactly what causes pitting and stress corrosion cracking in 304.
When to use 304L or 316L
The L (low carbon) variants have carbon below 0.03%, preventing chromium carbide precipitation during welding. Use L grades for fabrications welded in sections over 5 mm thick, or for any application where the weld heat-affected zone will see a corrosive environment. Normal 304 and 316 weld fine in thin sections.
Common specification mistakes
- Specifying 304 for coastal or marine equipment - within 2 years of installation you'll see rust stains and pitting. Always use 316 within 5 km of the sea.
- Assuming 316 is corrosion-proof - it isn't. Hot concentrated chlorides (seawater above 60C, pulp bleach plants) will still pit 316. Step up to 2205 duplex or 6Mo alloys for these.
- Using regular 304 or 316 for welded pressure vessels - carbide precipitation in the HAZ leaves a corrosion-vulnerable strip. Specify L grades for welded work.
- Confusing magnetic behaviour with grade - both 304 and 316 can become slightly magnetic after cold working (forming, machining). A magnet test alone doesn't distinguish them.
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Frequently Asked Questions
Is 316 stainless steel better than 304?
316 is better than 304 in chloride environments (marine, salt exposure, pools) because its 2% molybdenum content resists pitting corrosion. In non-chloride environments, both perform identically and 304 is 30-50% cheaper. Choose based on environment, not a blanket 'better' label.
Can I use 304 instead of 316 to save money?
Yes, if chloride exposure is not a concern. For indoor use, food contact without salt brines, and general architectural applications, 304 performs as well as 316 at 30-50% lower cost. Never substitute 304 for 316 in marine, chemical, or de-icing-salt environments.
What is the difference between A2 and A4 stainless fasteners?
A2 stainless fasteners use 304-equivalent composition per ISO 3506. A4 uses 316-equivalent composition with added molybdenum. Specify A4-70 or A4-80 for marine and chloride-exposed fasteners. A2-70 suits general engineering.
Will 316 stainless rust?
316 resists corrosion in most environments but can still rust given enough time, high temperature chloride brines, mechanical damage that breaks the passive oxide layer, or contamination with carbon steel particles (which cause cross-contamination rust). Passivation treatment helps restore the protective layer after fabrication.
Is 316L weldable?
316L is the preferred choice for welded 316 fabrications. Its low carbon content (below 0.03%) prevents chromium carbide precipitation during welding, so the heat-affected zone retains its corrosion resistance. Use 316L filler rod. Standard 316 welds fine in thin sections under 5 mm.
What are the main differences in chemical composition between 304 and 316 stainless steel according to 304 vs 316 Stainless Steel: Key Differences (UK Reference)?
According to 304 vs 316 Stainless Steel: Key Differences (UK Reference), 304 contains 8% nickel, no molybdenum, and has 18% chromium, while 316 includes 2% molybdenum, 12% nickel, and 17% chromium.
Which grade of stainless steel is more suitable for environments with high chloride exposure based on the information in 304 vs 316 Stainless Steel: Key Differences (UK Reference)?
Based on 304 vs 316 Stainless Steel: Key Differences (UK Reference), 316 stainless steel is better suited for environments with high chloride exposure due to its added molybdenum content, which provides superior resistance against chloride-induced pitting and crevice corrosion.
What are the typical price ratios between 304 and 316 stainless steel as mentioned in 304 vs 316 Stainless Steel: Key Differences (UK Reference)?
According to 304 vs 316 Stainless Steel: Key Differences (UK Reference), the typical price ratio is 1.0x for 304 and 1.3-1.5x for 316, indicating that 316 stainless steel is more expensive.
What are some common variants of 304 and 316 stainless steel discussed in 304 vs 316 Stainless Steel: Key Differences (UK Reference)?
In 304 vs 316 Stainless Steel: Key Differences (UK Reference), the common variants mentioned include 304L for lower carbon content making it easier to weld thick sections, and similarly, 316L is used for applications requiring enhanced weldability.
How do UK engineers typically choose between 304 and 316 stainless steel based on the information in 304 vs 316 Stainless Steel: Key Differences (UK Reference)?
UK engineers often decide to use 304 stainless steel for general applications where chloride exposure is minimal, given its lower cost of about 30-50% less than 316. For environments with high chloride content or aggressive chemical conditions, they opt for 316 due to its superior corrosion resistance.