When should a facade be specified in 316L rather than 304?
Specify 316L wherever chlorides reach the surface, and 304 where they do not. Coastal elevations, marine atmosphere and elevations beside roads treated with de-icing salt are 316L work. Interior cladding, ceilings, trim and general inland exposure are served by 304 without loss of service life.
The mechanism, not the preference
316L carries 2-3% molybdenum, which stabilises the passive film exactly where chloride ions try to break it down. That is why the grade question is answered by exposure, and why a magnet or a visual check cannot answer it.
Distance from the sea is a proxy
A tower 200 m inland but downwind of surf spray behaves like a coastal site. An enclosed atrium in the same building behaves like a dry interior. Altitude, prevailing wind and neighbouring structures all shift the answer.
| Exposure | Default grade |
|---|---|
| Heated interior, dry inland | 304 |
| Urban inland, moderate humidity | 304, 316L where welded |
| Coastal beyond 1 km, industrial | 316L |
| Marine atmosphere, surf zone | 316L minimum |
Where a welded element sits in a humid interior, 316L is usually the cheaper decision over the life of the building, because weld-adjacent staining appears within a season on 304.
Are you looking for a reliable manufacturer？
We can quickly provide customers with market analysis, technical support and customized services.