303 Stainless vs 304 Stainless
303 and 304 are the two most common austenitic stainless grades, and the choice almost always comes down to one question: are you machining a lot of parts, or do you need corrosion resistance and weldability?
The verdict
Choose 303 when you are turning or milling high volumes of non-welded parts (fittings, shafts, fasteners) and want fast, clean machining with good tool life. Choose 304 when the part must be welded, formed, or exposed to moisture, chemicals, or food contact. The added sulfur that makes 303 machinable is exactly what hurts its corrosion resistance and weldability versus 304.
Side-by-side data
| Property | 303 Stainless | 304 Stainless |
|---|---|---|
| Category | Stainless Steel | Stainless Steel |
| Density (g/cm³) | 8.0 | 8.0 |
| Tensile strength (MPa) | 515 | 515 |
| Yield strength (MPa) | 240 | 215 |
| Elongation (%) | 50 | 40 |
| Hardness | 228 HB | 201 HB |
| Max service temp (°C) | 870 | 870 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 16 | 16 |
| Typically used for | Machined fittings & fasteners | General corrosion-resistant parts |
Which should you choose?
Choose 303 Stainless if…
- You are screw-machining or CNC-turning parts in volume and want chip-breaking, fast feeds, and longer tool life
- The part is mechanically assembled (threaded, pressed, or bolted) rather than welded
- Geometry is complex with tight tolerances where machinability cuts cycle time and scrap
- Service environment is mild/indoor and not exposed to chlorides, acids, or food contact
- Typical uses: shafts, bushings, gears, nuts, bolts, valve and pump components
Choose 304 Stainless if…
- The part must be welded — 303's sulfur causes hot cracking and porosity, while 304 welds readily
- It will see moisture, washdown, chlorides, mild acids, or outdoor exposure
- Food, beverage, pharma, or sanitary contact where cleanability and corrosion margin matter
- You need to deep-draw, bend, or form sheet/tube without cracking
- You want a single grade available in every form (sheet, plate, tube, bar, wire, fittings)
Key differences that matter
- The only real chemistry difference is added sulfur (and sometimes selenium) in 303; everything else follows from it.
- 303 machines far better — sulfide inclusions break chips and reduce tool wear, which is its entire reason to exist.
- Those same inclusions are corrosion initiation sites, so 303 has noticeably lower pitting and crevice resistance than 304.
- 303 is generally considered non-weldable for structural joints; 304 is one of the most weldable stainless grades.
- Mechanical strength is essentially similar in the annealed condition — pick on processing and environment, not strength.
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Open the Material SelectorGet a Quote →Frequently asked questions
Is 303 stainless stronger than 304?
No meaningful difference. In the annealed condition their yield and tensile strengths are roughly comparable; both are non-hardenable by heat treatment and work-harden similarly. Strength is rarely the deciding factor — choose on machinability versus corrosion/weldability instead.
Which is cheaper, 303 or 304?
Raw bar pricing is close, often within a few percent. But total part cost can favor 303 for machined components because faster machining and longer tool life lower the per-piece cost. For welded or formed parts, 304 is the cheaper path overall.
Can I weld 303 stainless?
Not recommended for load-bearing joints. The free-machining sulfur promotes hot cracking and porosity. If you must weld it, use a 312 filler and expect reduced joint quality. If welding is required, switch to 304, which welds cleanly with standard 308/308L filler.
Does 304 resist corrosion better than 303?
Yes, clearly. The sulfide inclusions that make 303 easy to machine act as pitting and crevice corrosion sites. 304 has better resistance to moisture, chlorides, and mild acids. For washdown, marine-adjacent, or food environments, 304 (or 316) is the safer choice.
Can both be passivated and used for food contact?
304 is the standard food- and sanitary-contact grade and passivates well. 303 can be passivated but its inclusions leave it more corrosion-prone and harder to fully clean, so it is generally avoided for direct food, beverage, or pharma contact.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.