316 is the stainless you use when salt or chemicals are in the picture. It adds molybdenum to the 304 recipe, and that one change makes it far more resistant to pitting from salt water, coastal air, chlorinated water and many process chemicals. Boat builders, Gulf Coast fabricators, food processors and chemical plants all specify it for that reason. We source 316 and 316L in sheet, plate, bar, tube and pipe and arrange the cut.
What 316 stainless is
316 is an austenitic stainless with nominally 16–18% chromium, 10–14% nickel and 2–3% molybdenum. The molybdenum strengthens the passive film against chloride attack, which is what causes pitting and crevice corrosion in salt environments.
Like 304, it is non-magnetic when annealed and cannot be hardened by heat treatment. 316L is the low-carbon version for welding, and dual-certified 316/316L is what you will usually receive.
316 stainless properties
| Property | Value | What it means in the shop |
|---|---|---|
| Tensile strength | 75 ksi minimum (316L: 70) | Same strength class as 304 |
| Yield strength | 30 ksi minimum (316L: 25) | Forms like 304, work hardens as fast |
| Hardness | 95 HRB maximum | Annealed; hardens with cold work |
| Density | 0.29 lb/in³ (8.0 g/cm³) | Essentially the same weight as 304 |
| Weldability | Excellent | Use 316L filler to keep the moly in the weld |
| Machinability | Fair to poor | A bit tougher to cut than 304 |
| Corrosion resistance | Excellent in chlorides | Resists salt water pitting far better than 304 |
Minimums per ASTM A240. Mill certs show actual tested values.
Typical uses
- Boat fittings, rails, hardware and fasteners
- Coastal architecture, handrails and outdoor fixtures near salt water
- Chemical and pharmaceutical process equipment
- Food processing that uses brines or chlorinated cleaners
- Oilfield and offshore parts in salt or produced-water service
Common finishes and conditions
Sheet comes in 2B mill finish or polished #4 brushed. Plate is typically hot rolled, annealed and pickled. Bar comes cold finished or turned and polished, and tube and pipe either welded or seamless, with polished options for sanitary and railing work.
In marine and coastal work, surface finish matters as much as grade. A smoother finish sheds salt and resists tea staining better than a rough one, so a polished 316 railing outlasts a mill-finish one in the same spot.
316 vs 304 stainless
304 is the default and handles most indoor and inland work. 316 earns its extra cost wherever chlorides are present: salt water, spray from the Gulf, pool and spa environments, de-icing salts and many chemical processes. Strength is essentially the same. Welding, forming and handling are close enough that a shop set up for 304 can run 316 with the right filler.
| 316 | 304 | |
|---|---|---|
| Molybdenum | 2–3% | None |
| Nickel (nominal) | 10–14% | 8–10.5% |
| Chloride pitting resistance | Good | Moderate |
| Strength (A240 min) | 75 / 30 ksi | 75 / 30 ksi |
| Filler metal | 316L | 308L |
Welding and machining 316
Weld 316 with 316L filler, not 308L. A 308L weld on 316 leaves a weld with no molybdenum, and it will pit first in salt service. Use 316L base metal or dual cert for heavy welded parts, keep heat input low, and remove heat tint by pickling or passivating on anything that goes in the water.
316 machines a little harder than 304. It is gummier and work hardens quickly. Sharp carbide, rigid setups, steady feed and good coolant keep it from hardening ahead of the tool.