304 vs 316 stainless steel: which grade does your part need?
The difference between 304 and 316 stainless, when the extra molybdenum in 316 is worth it (salt, chlorine, marine, medical), and when 304 is the cheaper right answer.
Quick answer: 304 and 316 are the two workhorse austenitic stainless grades. 304 is the general-purpose default; 316 adds 2 to 3 percent molybdenum, which buys real resistance to chlorides, salt and marine environments. Spec 316 for coastal, food wash-down, pharma and anything that sees salt or chlorine. Use 304 everywhere else, because 316 costs roughly 20 to 40 percent more for corrosion resistance you may not need.
The difference is molybdenum
Both are 18/8-family austenitic stainless: corrosion-resistant, non-magnetic, tough, weldable. The one metallurgical difference that matters to a buyer is the 2 to 3 percent molybdenum in 316, which is what lets it shrug off chlorides and salt that would pit 304.
| Property | 304 | 316 |
|---|---|---|
| Corrosion resistance | Good, general purpose | Better, resists chlorides and salt |
| Key difference | Baseline | Adds 2 to 3% molybdenum |
| Cost | Baseline | Roughly 20 to 40% more |
| Best for | Indoor, general, dry food | Marine, coastal, wash-down, pharma, medical |
| Weld / machine | Good | Good |
When to spec 316
Anything that sees salt, chlorine or a wash-down line. Coastal and marine parts (a Vancouver or Halifax job), food and dairy equipment that gets sanitized daily, pharma, and medical. The shop that quotes 304 to save a couple dollars a pound is the shop whose part pits before the warranty is up. In a chloride environment, the molybdenum is the whole point.
When 304 is the right (cheaper) answer
Dry indoor parts, general structural stainless, architectural work out of the salt, and food contact that does not involve constant chloride wash-down. Do not pay the 316 premium for a dry indoor bracket. That is money spent to impress a spec sheet, not to make the part last.
Passivation applies either way
Whichever grade you pick, machining and grinding embed free iron in the surface that rusts and makes "stainless" look like it failed. Passivation to ASTM A967 removes it and restores the corrosion resistance. It is a normal final step on any machined stainless part, covered in what is passivation.
What to send for a quote
Your part, the grade (304 or 316, or tell us the environment and we will flag it), quantity and any finish or passivation spec. Request quotes from Canadian shops tooled for stainless.
FAQ
What is the main difference between 304 and 316?
The molybdenum in 316 (2 to 3 percent), which gives it much better resistance to chlorides, salt and marine environments. Otherwise they are similar austenitic stainless grades.
Is 316 worth the extra cost?
For salt, chlorine, marine, pharma and wash-down service, yes, it prevents pitting that would ruin a 304 part. For dry indoor and general work, no, 304 does the job for less.
Can you weld 304 and 316?
Both weld well, usually TIG for appearance and corrosion resistance. Use a matching or over-alloyed filler, and passivate after to restore the surface.
Does stainless steel rust?
It resists rust but is not rust-proof. Chlorides pit 304; free iron from machining rusts either grade until passivated. Grade selection and passivation together keep it clean.
Which stainless is best for food or medical?
316 for wash-down, chloride exposure and implantable or surgical work; 304 is acceptable for many dry food-contact parts. Both should be passivated for these uses.
Last reviewed: July 2026. Related reading: 6061 vs 7075 aluminum and what is passivation.
Request quotes for your part →