Material
Stainless 316 & 316L Parts
The chloride and saltwater grade, when 304 isn’t enough.
316 is the stainless to reach for when 304 would eventually pit: a few percent of molybdenum buys real resistance to chlorides, which means salt water, road salt, coastal air, and aggressive washdown. 316L is the low-carbon version for welded parts, where it resists the corrosion at the weld that standard 316 can lose. It machines and finishes much like 304, just slower, so it is specced when the environment demands it rather than by default. Put the grade on your print and send it through the quote form, and a quote comes back in 24-48 hours.
Updated June 2026
Stainless 303 / 304
Corrosion resistance for food, fluid, marine, and outdoor hardware. 303 trades a little of that for easier cutting.
What the molybdenum buys
The difference between 316 and 304 is a few percent of molybdenum. That addition resists the pitting and crevice corrosion that chlorides cause, which is exactly what beats ordinary stainless: salt water, road salt, coastal air, brine, chlorine and bleach washdown, and many process chemicals. Where 304 tea-stains and then pits, 316 holds.
In every other respect it is a close cousin of 304: the same austenitic family, the same bright look, similar strength, and similar machining behavior. It is not stronger than 304 and it cannot be hardened by heat treatment, so 316 is a corrosion choice, not a strength choice. When a part has to be both corrosion-resistant and strong, that is the job of 17-4 PH instead.
316 vs 316L, and when the L matters
The L in 316L means low carbon (under 0.03%), and the place it earns its keep is at a weld. Heating standard 316 in the weld zone can let chromium carbides form along the grain boundaries, leaving those boundaries short of chromium and prone to corrode, a condition called sensitization. 316L keeps the carbon low enough to avoid it, so the weld resists corrosion as well as the rest of the part.
The rule is simple. Anything welded into an assembly, or living in genuinely aggressive media, should be 316L. A part that is not welded is fine in plain 316. If the print does not say which, describe whether the part gets welded and the grade gets confirmed before pricing. Either way the cost and machining are close, so the choice is about the weld, not the budget.
What gets made from it
316 shows up wherever rust is the enemy and chlorides are in the picture: marine and coastal hardware, fittings and fasteners, pump and valve parts, chemical and process components, and food, pharmaceutical, and medical equipment. Turned parts like fittings and shafts, and milled parts like flanges, brackets, and housings, all come in 316 when the service calls for it. Typical tolerances match the rest of the site: ±0.005 in on milled features and ±0.001 in on critical turned diameters.
One honest trade to keep in mind: 316 cuts slower and gummier than free-machining 303, so a turned part that will never see a chloride is usually cheaper in 303 or 304. Reserve 316 for the parts that actually need it. Describe the environment in the quote notes and the grade gets flagged, so you are not paying for molybdenum a part will never use.
Passivation, finishes, and the magnet question
Even on 316, passivation matters. Machining can leave traces of free iron on the surface, and that iron, not the stainless, is what rust-stains first. A passivation bath, commonly specced to ASTM A967, strips it so the chromium-oxide layer can do its job, and it is standard practice on marine, food, and medical parts. Where a part has to be ultra-clean or sterilizable, electropolishing is specified with it; bead blast gives a uniform matte, and brushed or polished finishes are there where looks matter.
And the magnet test proves nothing here. Fully annealed 316 is essentially non-magnetic, but machining and cold work make the surface mildly magnetic, just as they do on 304. A faint pull on a magnet is normal and not a sign of the wrong grade. If a true non-magnetic requirement applies, call it out on the print so the material and process suit it.
Questions
Before you send a job.
01 What makes 316 better than 304?
Molybdenum. A few percent of it gives 316 real resistance to the chloride pitting and crevice corrosion that 304 eventually loses: salt water, coastal air, road salt, brine, and chlorine or bleach washdown. Otherwise they are close cousins, the same austenitic family with similar strength and machining. 316 costs more and cuts slower, so it earns its place where chlorides are present.
02 Should I spec 316 or 316L?
316L is the low-carbon version, and the difference matters at welds: standard 316 can sensitize and corrode in the weld zone, while 316L resists it. So 316L for anything welded into an assembly or in aggressive service, and plain 316 for an unwelded part. If the part gets welded, put the L on the print. Cost and machining are close either way.
03 Is 316 worth it over 303 or 304 for a turned part?
Only if chlorides are in play. 303 cuts fastest and is cheapest for turned fittings and shafts that will not see salt or harsh washdown, and 304 covers general and food work. Reach for 316 when the part lives in marine, coastal, chemical, or chlorine-washdown service. Describe the environment in the quote notes and the grade gets flagged before pricing.
04 Is 316 food-safe and medical-grade?
316 and 316L are standard choices for food, pharmaceutical, and medical hardware because they resist the cleaning chemicals and fluids that would corrode lesser grades. Passivation, and electropolishing where a sterilizable surface is needed, are specified with the part. Note the surface requirement on the print and it is quoted with the job.
05 Is 316 magnetic?
Mostly not. Fully annealed 316 is essentially non-magnetic, but machining and cold work make the surface slightly magnetic, just like 304. A faint magnet pull is normal and not a sign of the wrong grade. If a hard non-magnetic requirement applies, note it on the print so the grade and process are chosen to suit.
Related
Where to go next.
Stainless 303 & 304
The free-machining and general-purpose grades.
View →Stainless Steel
The grade guide: 303, 304, 316, and 17-4.
View →Stainless 17-4 PH
When stainless also has to be strong.
View →Passivation
Removes free iron so stainless doesn’t rust-stain.
View →Custom Fittings
Corrosion-resistant fittings turned to print.
View →Get a Quote
Describe the environment; grade flagged in 24-48 hours.
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