What differs
Both are austenitic stainless steels. 316L adds molybdenum (Mo) for better pitting and chloride resistance, at a higher cost. For vacuum chambers, both meet normal vacuum and welding requirements.
When to choose 316L
Coating processes with corrosive atmospheres, contact with acids, chlorides, or a drawing that explicitly specifies SUS316L. For standard semiconductor vacuum chambers, 304L is the mainstream choice.
What we do
We stock and fabricate both 304L and SUS316L; grade and surface finish follow your drawing. Material certificates ship with the unit, and incoming material is checked against the specification before release.
Not sure which to pick? Send your drawing and note the operating environment (process, atmosphere, temperature) — we will include a material recommendation with our DFM review.