--- title: "304 vs 316 Stainless Steel: Composition, Corrosion, Cost" source: "https://www.laxconsteels.com/304-vs-316-stainless-steel/" description: "AISI 304 and 316 compared on composition, PREN, chloride limits, strength, welding and cost, with the rule for choosing between them." --- # 304 vs 316 Stainless Steel: Composition, Corrosion Resistance, Strength and Cost Published 4 September 2026 8 min read AISI 304 and AISI 316 are the two austenitic stainless steels that account for most of the stainless bar, plate and tube bought in the world. They share the same structure, the same fabrication behaviour and, in the annealed condition, the same specified minimum strength. They differ in one alloying decision: 316 contains 2.0 to 3.0 percent molybdenum, and carries more nickel to keep the structure austenitic in its presence. That addition raises the resistance of 316 to chloride pitting and crevice corrosion, and raises its price. The choice between the two grades is therefore a question about the chlorides the part will meet in service, not about strength, machinability or appearance, in which the two are effectively the same steel. ## The difference in one table *AISI 304 and AISI 316 compared* | Property | AISI 304 (1.4301, S30400) | AISI 316 (1.4401, S31600) | | --- | --- | --- | | Chromium | 18.0 to 20.0 percent | 16.0 to 18.0 percent | | Nickel | 8.0 to 10.5 percent | 10.0 to 14.0 percent | | Molybdenum | none specified | 2.0 to 3.0 percent | | Carbon, maximum | 0.08 percent (0.03 in 304L) | 0.08 percent (0.03 in 316L) | | PREN at the composition window | 18.0 to 21.6 | 22.6 to 29.5 | | Minimum tensile strength, annealed bar (ASTM A276) | 515 MPa | 515 MPa | | Minimum 0.2 percent yield, annealed bar | 205 MPa | 205 MPa | | Density | 7.93 g/cm³ | 7.98 g/cm³ | | Magnetic response, annealed | essentially none | essentially none | | Chloride tolerance in potable water at ambient temperature (Atlas Steels guidance) | about 200 mg per litre | about 1,000 mg per litre | | Relative cost | base | higher, by the molybdenum and the extra nickel | ## Composition 304 is the 18/8 steel: 18 to 20 percent chromium, 8 to 10.5 percent nickel, carbon limited to 0.08 percent, and no deliberate molybdenum. 316 lowers the chromium window to 16 to 18 percent, raises nickel to 10 to 14 percent and adds 2 to 3 percent molybdenum. The lower chromium is deliberate: molybdenum is a ferrite former, and holding the austenitic structure with molybdenum present costs nickel, so the alloy is rebalanced rather than simply added to. Both grades exist in a low-carbon L form with carbon limited to 0.03 percent, specified where the part is welded and then exposed to a corrosive environment, and 316 also exists as 316Ti, stabilised with titanium for the same purpose at higher service temperatures. The full composition windows and the EN, JIS and UNS designations for both are in the [AISI 304](https://www.laxconsteels.com/grades/aisi-304/) and [AISI 316](https://www.laxconsteels.com/grades/aisi-316/) grade pages. ## Corrosion resistance Both grades depend on the same chromium oxide film. What molybdenum changes is the film's resistance to local breakdown by chloride ions, which is the mechanism of pitting and crevice corrosion. The pitting resistance equivalent number, PREN = Cr + 3.3 Mo + 16 N, states the difference: 304 computes to 18.0 to 21.6 across its composition window and 316 to 22.6 to 29.5, so the poorest 316 heat still outranks the best 304 heat. In practice the guidance published by the stainless steel industry puts 304 at roughly 200 mg per litre of chloride in ambient potable water and 316 at roughly 1,000 mg per litre before pitting becomes likely, with both limits falling as temperature rises. Neither grade is a seawater material: at 19,000 mg per litre of chloride, 316 pits in crevices and under deposits, and the selection moves to [duplex](https://www.laxconsteels.com/products/duplex-steel/) or super duplex grades. In atmospheres, 304 is used inland and 316 within a few kilometres of a coast, in de-icing salt spray, and around swimming pools. In non-chloride acids the two are close; 316 has the advantage in dilute sulphuric and in organic acids, which is why it is the default in chemical and pharmaceutical process equipment. ## Strength and fabrication ASTM A276 specifies the same minimum properties for annealed bar in both grades: 515 MPa tensile strength, 205 MPa yield strength, 40 percent elongation. Mill certificates for annealed round bar commonly record 550 to 650 MPa tensile for either grade. Both work harden at the same rate, both are non-magnetic in the annealed condition and become weakly magnetic when cold worked, and both are welded with matching filler by every common process; the L grades are chosen for welded fabrication that will see corrosive service, because carbon at 0.08 percent can precipitate as chromium carbide beside a weld and leave a chromium-depleted zone. 316 machines slightly less freely than 304, and neither approaches the free-machining [303](https://www.laxconsteels.com/grades/aisi-303/). Both are used from cryogenic temperatures to about 870 degrees Celsius in intermittent service; for continuous service above 425 degrees Celsius the stabilised or H grades are specified instead. ## Cost 316 costs more than 304 for two reasons that both trace to the composition table: 2 to 3 percent molybdenum, which is the more expensive of the two alloying metals, and 2 to 3.5 percentage points more nickel. The premium moves with the nickel and molybdenum markets and is quoted per tonne at the time of the enquiry rather than as a fixed ratio. The premium buys chloride resistance and nothing else, so on a part that will never meet chlorides it buys nothing. ## Where each grade is specified 304 is specified for kitchen and food equipment, dairy and brewery vessels, indoor architecture and trim, tanks and hoppers for dry or non-chloride product, general machined components, fasteners in inland service, and any part where the corrosion environment is water, steam, mild acid or air away from the coast. 316 is specified for coastal and marine architecture, boat fittings and shafting above the waterline, chemical and pharmaceutical process plant, pulp and paper equipment, surgical instruments and implants (as 316L), heat exchangers in cooling water with a chloride content, and any part that sees de-icing salt or process brine. The rule is short: where the environment contains chlorides at a concentration or a temperature that 304 has been known to pit in, 316 is the grade; everywhere else 304 is the grade, and the saving is real. ## Both grades as bar Laxcon Steels melts both grades and supplies them as [hot rolled round bar](https://www.laxconsteels.com/products/hot-rolled-round-bars/) from 16 to 125 mm, [bright bar](https://www.laxconsteels.com/products/bright-bars/) from 5 to 115 mm, [flat bar](https://www.laxconsteels.com/products/hrap-flat-bars/), [angle](https://www.laxconsteels.com/products/hrap-equal-angles/) and [threaded bar](https://www.laxconsteels.com/products/threaded-bars/), with the heat analysis on the certificate against the composition window of the grade ordered. The [304 guide](https://www.laxconsteels.com/304-stainless-steel-quality-guide-why-its-industry-standard/) covers the 304 variants and service limits in detail, and the [PREN reference](https://www.laxconsteels.com/pren-stainless-steel-what-your-grade-guarantees/) ranks both grades against the rest of the stainless family. ## Sources - ASTM A276/A276M, Standard Specification for Stainless Steel Bars and Shapes. - EN 10088-1, Stainless steels, list of stainless steels. - Atlas Steels, Technical Handbook of Stainless Steels: chloride limits for grades 304 and 316. - The composition windows and PREN values in the [Laxcon grade reference](https://www.laxconsteels.com/grades/).