Q03 — TECHNICAL ANSWER
SS 304 or SS 316 for Food-Grade Parts?
SS 304 covers most food-contact and washdown positions, and 316 is specified where chlorides are present. That is the whole decision in one line: if the position sees brine, salted product, coastal humidity or chlorinated cleaning chemistry, 316 earns its cost. If it does not, 304 does the same job for less.
What actually separates the two grades
Both are austenitic stainless steels and both resist general corrosion in food environments. The difference is molybdenum, which 316 contains and 304 does not. Molybdenum is what buys resistance to pitting and crevice corrosion in chloride-bearing conditions — and chlorides are the specific thing that defeats 304.
That is why the question is never really "which is better". 316 is better at one thing. If the position does not present that thing, the extra alloy content is paid for and not used.
The practical test is the environment rather than the product. A part handling dry grain in a mill and a part handling the same grain after a chlorinated washdown are in different chemical positions even though the product is identical.
When 316 is worth specifying
Brine, pickling and salted product put chlorides in direct contact with the part. Chlorinated cleaning chemistry does the same on a schedule, which is often the more damaging case because it reaches crevices the product never touches. Coastal humidity is a slower version of the same problem.
Pitting is what makes this matter on a food line specifically. General corrosion thins a part predictably; pitting puts a small deep hole in it, and a pit is a crevice that traps product and resists cleaning. A pitted surface fails hygienically before it fails structurally.
316L is the same grade with lower carbon, specified where the part is welded — the lower carbon reduces sensitisation in the weld region, which is where a welded stainless part usually corrodes first.
How we handle the choice
Where a drawing specifies a grade we manufacture to it. Where a drawing leaves the grade open, we raise it before cutting rather than substitute — because on a food-contact part this is a service-life decision, not a purchasing one, and it belongs with whoever owns the equipment.
We work in stainless steel 304, 316, 316L, 410 and 420. 410 and 420 are martensitic and harden by heat treatment, which puts them in wear positions rather than corrosion positions — a different question from this one.
If you are replacing an existing part and are not sure what it was made in, send it with photographs and tell us where it runs. The position usually settles the grade faster than testing the part does.
SS 304 and SS 316 — related questions
- Is 316 always the safer choice for food contact?
- Not always the sensible one. It is more resistant to chlorides, but where no chlorides are present the extra alloy content is paid for and never used. 304 covers most food-contact and washdown positions.
- What is the difference between 316 and 316L?
- Lower carbon in 316L, which reduces sensitisation in the weld region. Specify it where the part is welded, since that is where a welded stainless part usually corrodes first.
- Which grades do you machine?
- Stainless steel 304, 316, 316L, 410 and 420, alongside carbon and alloy steel, brass, phosphor bronze and aluminium. Other grades can be arranged on request.
- Can you advise the grade if our drawing does not state one?
- We will raise it before cutting rather than substitute. Tell us the position and the cleaning regime and that usually settles it — the environment decides the grade more often than the product does.
Send your drawing with the grade if it is specified, or tell us the position and the cleaning regime and we will confirm it with you first. An NDA can be arranged before any detailed technical exchange.