304 vs 316 Stainless Steel

Updated October 14, 2026

304 vs 316 side by side

316 is 304 with 2 to 3 percent molybdenum and more nickel. That one change raises chloride pitting resistance and costs more; strength, density and thermal behavior barely move. The table pulls the numbers from two producer data sheets and the British Stainless Steel Association (BSSA), with the basis of each figure stated.

Read the strength rows carefully. The 304/304L figures are the 304L minimums because the Rolled Alloys sheet (08/23) reports the dual certified product, while its 316/316L sheet (08/26) reports values that meet straight 316. Rolled Alloys states that controlled nitrogen additions let both L grades meet the straight grade properties, which is why most commercial plate is dual certified. Do not design to the table; take acceptance values from the AMS or ASTM spec on your drawing.

Choose 304 when, choose 316 when

Choose 304 or 304L when

• The part lives indoors, in a controlled bay or in clean fluid, and chlorides are not concentrated on its surface.
• The job is general hardware, brackets, enclosures, cryogenic plumbing or formed sheet, and cost and stock breadth matter.
• The drawing calls AMS 5513 sheet or AMS 5567 hydraulic tube and the design is already qualified on 304.

Choose 316 or 316L when

• The hardware sits in salt air, sea spray or a launch pad environment, or is washed down with chloride solutions, where pitting and crevice corrosion are the failure modes.
• Crevices cannot be designed out: lap joints, threaded fittings, clamps and gasketed flanges trap moisture and salts.
• Parts are welded and then exposed to corrosive service, in which case specify 316L.
• Magnetic permeability matters near sensors or instruments and the part is cold worked, since more nickel makes the austenite less prone to the strain-induced change.

If neither alloy is enough, the next step is not a better 300 series grade by default. Higher molybdenum austenitics, duplex grades and nickel alloys exist for that case; see nickel superalloys.

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Molybdenum, pitting and what PREN tells you

Molybdenum is the reason to pay for 316. Rolled Alloys states that it increases general corrosion resistance, improves chloride pitting resistance and strengthens the alloy in high-temperature service, and lists improved general and localized corrosion compared to 304/304L as a feature.

The pitting resistance equivalent number ranks grades by composition. The BSSA gives the common form as PREN = Cr + 3.3Mo + 16N, notes that some formulas weight nitrogen at 27 or 30 without changing the ranking much, and computes 17.5 to 20.8 for 1.4301 (304) and 23.1 to 28.5 for 1.4401/1.4404 (316/316L) from the EN composition limits. Two cautions from the same source matter for buyers:

• PREN cannot predict whether a grade suits a given application. It ranks; it does not qualify.
• Ranges from specified limits can understate the real number, because commercial heats carry residual nitrogen. If PREN is a design requirement, compute it from the heat analysis on the mill cert, not the spec range.

Our check of the 304 figure: chromium 19.5 plus 16 times 0.11 nitrogen gives about 21.3, a little above the 20.8 the BSSA table prints, so treat the top of that range as approximate. The gap between the two grades is the point: roughly 5 to 8 PREN units, almost all from molybdenum.

L grades, sensitization and welding

Specify the L grade whenever the part is welded and then sees corrosive service. Straight 304 and 316 allow up to 0.08 percent carbon; the L grades hold 0.03 percent. Heat from welding or brazing lets chromium carbides form at grain boundaries, the condition called sensitization, and the chromium-depleted zone beside them corrodes. The AMS 5513 scope makes the same point in spec language: the material is used for parts needing corrosion resistance up to 800 F, and welding, brazing or other exposure above 800 F during fabrication may reduce corrosion resistance.

• Dual certification removes most of the trade. Because nitrogen lets the L chemistry meet straight grade strength, a 304/304L or 316/316L cert satisfies both callouts on most PO lines. Confirm that your spec accepts a dual cert; some AMS documents control chemistry tightly.
• Weldability is good for both. Both producer sheets list good weldability and formability. The aerospace control is the weld procedure and welder qualification, for example AWS D17.1, covered on our sheet metal and aerospace welding page.
• Weld ferrite is intentional. ASSDA notes that austenitic welds carry a little ferrite for hot strength, and that its magnetic effect is usually insignificant because welds are a small part of a structure.
• Stress corrosion. NASA MSFC-STD-3029 states that 300 series austenitic stainless steels are generally resistant to stress corrosion cracking and groups them, in the unsensitized condition, in its Table I. Sensitization is the condition that takes a weldment out of that comfort zone.

Magnetic response after cold work

Neither alloy is reliably nonmagnetic once it has been cold worked. ASSDA states that 304 and 316 are generally regarded as nonmagnetic when annealed, but that cold worked material is attracted to a permanent magnet because deformation transforms part of the austenite to martensite. The effect is less marked in alloys with more austenite stabilizers such as nickel, which favors 316 at 10 to 14 percent nickel over 304 at 8 to 11 percent.

• Where it shows up: drawn tube, cold headed fasteners, bent brackets, spun or deep drawn parts and anything sold in a temper above annealed.
• The fix and its cost: ASSDA says solution annealing and water quenching removes the effect but also reduces tensile properties and may distort the part. Electrical demagnetizing does not reverse strain-induced martensite well.
• How to specify it: if permeability matters, state a maximum relative permeability and the test method on the drawing rather than writing nonmagnetic. ASSDA notes highly alloyed austenitics typically stay below a relative permeability of 1.02, a useful reference point when setting the limit.

Do not use a magnet at receiving inspection to tell 304 from 316. Both may pull, and both may not. Positive material identification by XRF or a lab chemistry check is the reliable way to confirm molybdenum is present.

Tubing, fittings and oxygen service

Both grades are standard tube materials, and the AMS tube specs are grade specific. Two numbers that often get lumped in with them cover different alloys:

If a drawing calls AMS 5557 or AMS 5556 for a 304 or 316 line, raise it with engineering before release; those are titanium and columbium stabilized grades. ASTM A269 tube is common in ground and facility systems, but its scope says mechanical property requirements do not apply below 1/8 inch inside diameter or 0.015 inch wall, so small instrument tube needs its acceptance stated another way. For tube stock and fittings, see aerospace tubing and fluid fittings.

Oxygen service. Grade choice is only part of an oxygen system decision. ASTM G94 is the guide for evaluating metals for oxygen service; its scope is the relative susceptibility of a metal to ignition and propagation of combustion, and it states it is not a specification for approving materials. Cleanliness, particulate, design velocity and soft goods usually decide whether a 304 or 316 line is safe. Clean to a stated level and package to hold it; see precision and oxygen cleaning and our oxygen cleaning service.

Specifications for each form

Use an AMS spec for flight hardware and the ASTM spec where the program allows commercial material. SAE titles and revisions below were read on SAE Mobilus in October 2026; confirm the current revision on ASSIST or SAE before release.

The base grades are in our stainless and specialty steels overview, which also covers passivation in more depth. For the precipitation hardening side of the stainless family, see 17-4 vs 15-5 PH stainless.

Machining, finishing and passivation

Machine both the same way: sharp tools, positive rake, constant feed and no dwelling, because austenitic grades work harden at the cut. Neither producer sheet we used gives cutting data, so set feeds and speeds from the shop's own experience with the heat in hand. Do not let a free-machining grade be substituted without engineering approval; it is a different alloy with its own spec.

• Passivate after machining. Call AMS 2700 with the method and the verification test. Do not assume one bath recipe fits both grades; flow the alloy to the processor. Detail is on the surface finishing page.
• Keep carbon steel off the part. Shared tooling, wire brushes and fixtures embed free iron that rusts in the first humid week. Passivation removes some of it; segregation prevents it.
• Coatings. Neither grade normally needs a coating for corrosion. Where a dissimilar metal joint creates a galvanic couple with aluminum, the aluminum side is the one to protect; see chemical conversion coating and paint and primer systems.

Cost and availability drivers

Expect 316 to cost more than 304 in the same form, and expect the gap to move with nickel and molybdenum markets. We do not quote material prices; these are the drivers:

• Alloy content. 316 carries 2 to 3 percent molybdenum and 10 to 14 percent nickel against 304's 8 to 11 percent nickel. Mills commonly price those elements through alloy surcharges that change month to month.
• Market size. Rolled Alloys calls 304 the original 18-8 stainless and says it is produced in greater quantity than any other austenitic stainless steel. Commercial stock of both is deep; AMS-certified stock in thin gauges, small tube sizes and large bar is a much smaller pool.
• Certification. AMS material with full traceability costs more than commercial ASTM product. A dual certified heat that meets both AMS and ASTM requirements is the easiest to source.
• Specialty metals. Both grades are DFARS specialty metals, so contracts carrying 252.225-7009 restrict the melt source. See DFARS specialty metals.
• Processing. Annealing to restore permeability, passivation and oxygen cleaning each add a step, a cert and lead time.
• Certified surplus. Remnant plate, bar and tube with traceable certs can shorten lead time when the cert shows the right spec and revision.

Callouts for the drawing and PO

Name the grade, spec and form, and add the conditions that change the outcome: L grade, permeability, passivation and cleanliness. Examples:

• Welded bracket for pad service: MATL: CRES 316L SHEET PER AMS 5507. PASSIVATE PER AMS 2700 AFTER WELDING AND FINAL MACHINING.
• Indoor sheet metal enclosure: MATL: CRES 304 SHEET PER AMS 5513 (or ASTM A240 TYPE 304 where commercial material is allowed).
• Hydraulic line: TUBE: CRES 304 PER AMS 5567, with size, wall and any cleanliness level stated.
• Oxygen line: TUBE: CRES 316 PER AMS 5573, CLEAN FOR OXYGEN SERVICE TO the level your system spec requires, with packaging stated.
• Sensor mount: MATL: CRES 316 BAR PER AMS 5648. MAX RELATIVE PERMEABILITY stated with the test method.

On the PO require the spec and revision, the mill cert with heat number and chemistry showing molybdenum for 316, dual certification acceptance if you allow it, DFARS 252.225-7009 compliance where the contract carries it, and the passivation or cleaning cert. Our certs and traceability page shows what to check. For a related comparison in aluminum, see 6061 vs 7075 aluminum.

Get 304 or 316 material quoted

Send the spec, form, size and any cleaning or permeability requirement through a certified material request. We source AMS and ASTM 304 and 316 sheet, bar and tube from qualified suppliers with traceable mill certs, confirm the grade and chemistry on the cert before shipment, and can add machining, passivation and oxygen cleaning on the same PO. A person replies within one business day. See also plate and sheet, bar and rod and the materials hub.

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Related

• Stainless and Specialty Steels for Aerospace Parts
• 17-4 PH vs 15-5 PH Stainless Steel
• Precision Cleaning and Oxygen Service Cleaning
• Aerospace Surface Finishing: Specs, Callouts and Pitfalls

Sources

• Rolled Alloys, 304/304L data sheet (08/23): chemistry, ASTM A240 minimums, physical properties
• Rolled Alloys, 316/316L data sheet (08/26): chemistry, ASTM A240 minimums, molybdenum effects
• British Stainless Steel Association, Calculation of pitting resistance equivalent numbers (PREN)
• Australian Stainless Steel Development Association, Magnetic effects of stainless steels
• SAE Mobilus, AMS5513L 304 sheet, strip and plate, solution heat treated (scope and revision)
• SAE Mobilus, AMS5524 316 sheet and strip
• SAE Mobilus, AMS5507 316L sheet, strip and plate
• SAE Mobilus, AMS5567 304 hydraulic tubing
• SAE Mobilus, AMS5573 316 tubing
• SAE Mobilus, AMS5556 347 tubing
• SAE Mobilus, AMS5639 304 and AMS5648 316
• Aircraft Materials, 316 and 316L specifications and composition
• ASTM A269/A269M, seamless and welded austenitic stainless steel tubing for general service (scope)
• ASTM A276, stainless steel bars and shapes (scope)
• ASTM G94-22, Standard Guide for Evaluating Metals for Oxygen Service
• NASA MSFC-STD-3029 Revision A, section 4.4.2 ferrous alloys