Difference Between AISI 304 and AISI 316
AISI 304 and AISI 316 are austenitic stainless steels. The main difference is the molybdenum addition in 316, commonly specified at 2–3% by weight, which improves resistance to chloride pitting and crevice corrosion. Choose 304 for suitable general service; consider 316 when the environment justifies additional corrosion resistance. Neither grade is universally rustproof, and mechanical properties depend on the supplied condition.
For industrial buyers, comparing 304 stainless steel and 316 stainless steel means matching the material to the part, process and environment. Myriad’s guide focuses on the questions that matter when specifying foil, strip and coil: what contacts the surface, how the metal will be formed, and what evidence is needed before accepting a shipment.
A grade name alone does not define a finished component’s performance. The purchase specification must also identify dimensions, delivery condition, surface requirements and inspection criteria. This comparison separates established alloy differences from decisions that require application testing or a supplier’s written confirmation.
Table of Contents
What is the chemical difference between AISI 304 and AISI 316?
AISI 304 is a chromium–nickel stainless steel, while AISI 316 contains chromium, nickel and molybdenum. Both belong to the austenitic family. Molybdenum is the clearest compositional distinction for buyers evaluating chloride exposure; the grade number itself is not a general quality ranking.
The following table summarizes selected composition limits reported in ASSDA’s 304 guide and ATI’s 316 technical data sheet. Values are percentages by weight. These published references support comparison; the specified product standard and edition govern an actual order.
| Selected element | Type 304 / UNS S30400 | Type 316 / UNS S31600 |
| Chromium | 18.0–20.0% | 16.0–18.0% |
| Nickel | 8.0–10.5% | 10.0–14.0% |
| Molybdenum range | 0% | 2.0–3.0% |
| Carbon | 0.08% maximum | 0.08% maximum |
Sources: ASSDA’s 304 grade guide and ATI’s 316 data sheet, version 1, February 2014. This is a selected-element comparison, not a complete acceptance specification. Other standards and editions can use different limits.
AISI 304 stainless steel is often described as “18/8,” but that shorthand does not establish the exact chemistry of a coil. Likewise, a typical mill composition is different from a specification limit. Outokumpu’s Core range identifies 304/4301 as a general-purpose grade with good formability and weldability; its producer data should not be substituted for another supplier’s batch certificate.
Terms such as AISI 304 SS and AISI 316 SS are common abbreviations for the respective stainless steel grades. They do not indicate AISI approval of a supplier, factory or shipment. An order should state the applicable material specification and required certification separately.
ASTM A240 Material: Applications and Classifications
Is 316 stainless steel more corrosion resistant than 304?
316 stainless steel generally offers better resistance to chloride-induced pitting and crevice corrosion than 304 stainless steel. That advantage does not establish suitability for every saltwater or chemical environment. Temperature, concentration, deposits, crevices and surface condition can change whether either material performs acceptably.
According to Outokumpu’s corrosion guidance, stainless steel corrosion takes several forms, so material selection must consider the relevant damage mechanism. Localized attack matters particularly when a small pit could penetrate a thin component. A clean, accessible surface and a deposit-filled joint should not be treated as equivalent exposures.
316’s molybdenum addition provides an advantage in many chloride environments, but “marine grade” does not mean immune to seawater corrosion. Continuous immersion, stagnant liquid or warm salt deposits warrant a more detailed review. Higher-alloy materials may be necessary where neither aisi 304 nor 316 stainless steel provides sufficient resistance.
Chemical compatibility also needs more than an alloy ranking. Outokumpu’s corrosion tables specify that their data apply to annealed materials with normal microstructure and clean surfaces. A welded, contaminated or heavily worked part may not reproduce those reference conditions.
For a useful corrosion review, provide five inputs: the contacting medium, concentration, operating temperature, exposure pattern and cleaning procedure. Include abnormal conditions such as shutdown deposits or cleaning residues. Where service conditions are uncertain, representative testing can support the selection more effectively than a generic “304 versus 316” claim.
Three illustrative selection scenarios
Dry indoor formed component: 304 stainless steel is a reasonable candidate when the environment is mild and corrosion is not the limiting issue. Confirm the required forming behavior and final dimensions before approving the material.
Component exposed to saline washdown: aisi 316 stainless steel deserves evaluation where chloride exposure challenges 304 stainless steel. Review drainage, retained deposits and cleaning conditions before accepting the substitution.
Part in warm, stagnant chloride solution: Do not automatically select 316 stainless steel. Review both the alloy and component design, including whether a more resistant material or representative exposure test is needed.
These are selection examples, not customer case studies or guarantees for a particular service environment.
How To Find The Right Stainless Steel Supplier – Myriad Stainless Steel
What are the differences between 304 and 316 stainless steel in terms of strength, formability, and weldability?
Neither 304 nor 316 stainless steel is always stronger, harder or easier to form. Delivery condition and processing history must be included in the comparison. A cold-worked strip and an annealed sheet can have very different properties even when their grade designations are identical.
Ulbrich’s guide to stainless steel temper conditions explains how cold work changes strength and ductility. For a formed clip, spring or thin strip component, specifying only “half-hard” leaves important acceptance details unresolved. Agree on the relevant hardness or tensile requirements and the test method.
For example, a 0.05 mm strip trial should use the intended thickness, temper and rolling direction. A successful trial on thicker, softer sheet does not establish performance for the thinner production material. This is a process-control recommendation, not a claim that either grade has a universal minimum bend radius.
Both grades can be formed and welded, but the fabrication procedure still matters. Alleima’s welding guide addresses joint preparation, welding practice and post-weld treatment. Grade selection cannot compensate for an unsuitable procedure, surface contamination or unaddressed weld discoloration.
When should 304L or 316L enter the discussion?
Consider the low-carbon variants when welding and subsequent corrosion exposure make sensitization a concern. Outokumpu’s Supra range explains the improved resistance to intergranular corrosion after welding offered by low-carbon 316L. This is a separate selection question from choosing between the 304 and 316 alloy families.
Do not replace a specified grade with its L variant solely because the names look similar. Confirm the required chemistry, mechanical properties, product standard and design requirements. A dual-certified shipment must have evidence supporting both designations.
Can heat treatment or a magnet identify the grade?
304 and 316 are not hardened by conventional quench-and-temper treatment. Cold working can increase strength, while annealing can restore a softer condition. Heat treatment and cold reduction should therefore be considered part of the material specification, rather than inferred from the grade number.
A magnet is also an unreliable identification tool. ASSDA notes that annealed 304 is virtually non-magnetic but can become magnetic after cold working. Use traceable material documentation and an appropriate chemical identification method when distinguishing 304 from 316 matters.
Is AISI 316 worth the additional cost?
316 stainless steel commonly costs more than comparable 304 because its alloying requirements differ, including molybdenum. The actual premium must come from current, comparable quotations. A fixed percentage cannot reliably describe different thicknesses, widths, quantities, finishes and delivery conditions.
Compare quotations on the same basis before deciding that one grade offers better value. A narrow slit coil and a wider parent coil may carry different processing costs. Inspection, packaging, usable yield and delivery requirements can also affect the amount paid for material that is ready for production.
A practical purchasing calculation is: material and processing cost, plus expected fabrication loss, inspection, maintenance and replacement cost. These inputs should come from the buyer’s process and supplier quotations. Without those inputs, a numerical lifecycle-saving claim would be speculative.
304 stainless steel mremains a sensible candidate when it satisfies the application. 316 becomes a stronger candidate when its corrosion resistance addresses a documented exposure risk. Paying for 316 without checking temper, surface condition and dimensions can still leave the buyer with material that fails the production requirement.
Grade 304 Stainless Steel Foil– Myriad Stainless Steel
What should buyers specify for 304 or 316 foil, strip and coil?
Specify the grade together with measurable delivery and acceptance requirements. This helps suppliers quote comparable material and gives receiving inspection a clear basis for acceptance. For thin products, the dimensional and mechanical requirements deserve as much attention as the alloy name.
- Material: grade, applicable product standard and edition, and whether substitution or dual certification is acceptable.
- Dimensions: thickness, width, tolerances, and the agreed measurement method and sampling locations.
- Condition: annealed or cold-worked state, with required hardness or tensile properties where relevant.
- Surface and edges: finish, cleanliness, permissible defects, edge condition and burr limits where required.
- Coil format: inside diameter, outside diameter or weight limits, winding and packaging requirements.
- Inspection: required documents, traceability, test methods and any agreed sample approval before production supply.
For an illustrative 0.05 mm × 20 mm strip enquiry, the buyer should still specify the tolerances and delivery condition. Those nominal dimensions alone do not establish formability, coil handling or acceptable edge quality. The supplier should confirm the complete combination before an order is accepted.
For a quotation discussion with Myriad, provide the drawing or application description, dimensions, material condition, quantity and inspection requirements. The 304 stainless steel coil page provides related product context; use the contact page to discuss the actual specification. Availability and acceptance requirements should be confirmed for the quoted item.
ASTM A167: Composition, Properties, and Equivalent Grades
Frequently asked questions
What is the main difference between AISI 304 and AISI 316?
The main difference is 316’s molybdenum addition, commonly specified at 2–3%, which improves resistance to chloride pitting and crevice corrosion. Both are austenitic stainless steels; neither is automatically suitable for every corrosive environment.
Is 316 stainless steel always better than 304 stainless steel?
No. 316 stainless steel offers a useful corrosion-resistance advantage in many chloride exposures, while 304 stainless steel can meet less demanding requirements economically. Selection still depends on the environment, material condition and finished-part requirements.
Can 304 stainless steel be magnetic?
Yes. Cold-worked 304 stainless steel can show magnetic attraction even though annealed 304 stainless steel is virtually non-magnetic. A magnet cannot reliably verify whether a shipment is 304 or 316.
Are AISI 304 and AISI 316 rustproof?
No. Both resist corrosion under suitable conditions, but either can suffer attack when the exposure exceeds its capability. Surface contamination, retained salts and crevices can contribute to problems.
Can a buyer substitute 316 for 304 without further checks?
A substitution should be reviewed against the drawing and purchase specification. Confirm chemistry, mechanical condition, fabrication requirements and any design approvals before accepting it; additional corrosion resistance alone does not establish full equivalence.
Selection takeaway: Choose AISI 304 stainless steel or AISI 316 stainless steel by the service environment, then verify the supplied condition and specification. For foil, strip and coil, a clear enquiry and traceable inspection records are more useful than a broad claim that one grade is “best.”
ASTM A240 Type 304: Properties, Pricing, and Applications