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Precision Shims
Flange GuardsSS304 vs SS316 Shims: Which Grade Should You Use?
Short answer: use SS316 shims anywhere the shim will see seawater, salt spray, chlorides or chemicals, because the 2–3% molybdenum in 316 greatly improves resistance to pitting and crevice corrosion. Use SS304 shims for indoor or dry industrial machinery alignment, where they do the same job at a lower price.
SS304 and SS316 at a glance
| Property | SS304 (1.4301) | SS316 (1.4401) |
|---|---|---|
| Chromium | 18–20% | 16–18% |
| Nickel | 8–10.5% | 10–14% |
| Molybdenum | None | 2–3% |
| PREN (pitting resistance) | about 18–20 | about 23–28 |
| Density | about 7.9 g/cm³ | about 8.0 g/cm³ |
| Min. tensile strength (annealed) | 515 MPa | 515 MPa |
| Magnetic? | Non-magnetic when annealed; slightly magnetic after cold rolling | Non-magnetic when annealed; slightly magnetic after cold rolling |
| Common standards | ASTM A240 / A666, EN 10088-2 | ASTM A240 / A666, EN 10088-2 |
| Relative cost | Lower | Higher (molybdenum and extra nickel) |
Why molybdenum matters in the Gulf
Coastal plants, ports, desalination sites and offshore platforms in the UAE and GCC combine heat, humidity and airborne salt. Chlorides attack the passive film on stainless steel and start pits, often in the tight gap between a shim and a machine foot. Molybdenum in SS316 makes that film far more stable, which is why marine and offshore specifications usually call for 316 or 316L.
When SS304 is the right choice
- Pump, motor and gearbox alignment indoors or in dry plant rooms
- General fabrication, packing and spacing where corrosion risk is low
- Large quantities where cost matters and the environment is controlled
When to specify SS316 (or 316L)
- Ships, jetties, offshore and coastal installations
- Chemical, fertiliser, food and pharmaceutical plants with wash-down or chloride exposure
- Welded assemblies: choose 316L (low carbon) to avoid sensitisation at the weld
Thickness and form
Both grades are supplied as shim sheet, shim stock coil and pre-cut or slotted shims, typically from 0.025 mm up to about 3 mm. See our shim thickness chart (mm to inch).
Values are typical figures from published material standards and supplier data, for guidance only. Always check the mill test certificate and your design code for the exact grade you buy.
Need a price or stock check? Send the grade, size and quantity to sales@saifexindustries.com, WhatsApp +971 58 535 2330, or request a formal quote. See our SS316 marine-grade shims.
Or compare with SS304 shims.
Frequently asked questions
Is SS316 better than SS304 for shims?
For corrosion, yes. SS316 contains 2–3% molybdenum, which gives much better resistance to chlorides and seawater. Mechanically the two grades are similar, so SS304 is fine and cheaper for dry indoor use.
Can I use SS304 shims offshore?
It is not recommended. Salt spray and chlorides can pit SS304, especially in the crevice under a machine foot. Marine and offshore specifications normally require SS316 or 316L.
Are stainless steel shims magnetic?
Annealed SS304 and SS316 are essentially non-magnetic. Cold-rolled shim stock can become slightly magnetic, which does not affect corrosion resistance.
What is the difference between SS316 and SS316L?
316L has a lower carbon limit (0.03% max), which prevents carbide formation during welding. For unwelded shims, 316 and 316L perform the same.