Sodium Hydroxide Resistant O-Rings
Compatibility ratings for 7 O-ring materials in Sodium Hydroxide service
Caustic service inverts the usual hierarchy: EPDM rates A while FKM drops to C. For sodium hydroxide at concentration, EPDM, PTFE and FFKM are the reliable choices.
Sodium Hydroxide (Bases) compatibility with the seven most common O-ring elastomers, rated on the standard A/B/C/D scale: A = excellent, B = good, C = fair, D = not recommended. This data also appears in our interactive chemical compatibility chart and is available machine-readable at /api/chemicals.json.
| Material | Rating | Guidance |
|---|---|---|
| NBR | B | good — suitable for most applications |
| FKM | C | fair — conditional use, verify with testing |
| EPDM | A | excellent — recommended for continuous service |
| VMQ | C | fair — conditional use, verify with testing |
| PTFE | A | excellent — recommended for continuous service |
| FFKM | A | excellent — recommended for continuous service |
| HNBR | B | good — suitable for most applications |
Why These Ratings
- EPDM (A) — documented strengths include “Dilute acids and alkalis.”
- VMQ (C) — documented weaknesses include “Concentrated acids and alkalis.”
- PTFE (A) — documented strengths include “Virtually all chemicals.”
- FFKM (A) — documented strengths include “Virtually all chemicals except molten alkali metals.”
BasesService: Concentration & Temperature Notes
Caustic service inverts the usual hierarchy: EPDM outperforms FKM here (A versus C in our sodium- and potassium-hydroxide rows). Amine-containing bases are harder on FKM than hydroxides — FKM rates D in ammonia service. Hot caustic is dramatically more aggressive than cold; validate any caustic application above +50°C with immersion testing.
Recommended
- EPDM O-rings (A)
- PTFE O-rings (A)
- FFKM O-rings (A)
Use With Caution
- NBR O-rings (B)
- FKM O-rings (C)
- VMQ O-rings (C)
- HNBR O-rings (B)
Avoid
No material is rated D for this chemical.
Related Chemicals (Bases)
Frequently Asked Questions
Is Sodium Hydroxide compatible with FKM (Viton) O-rings?
FKM is rated C for Sodium Hydroxide: fair — conditional use, verify with testing. Ratings are general guidelines; concentration, temperature and exposure time all affect real-world compatibility, so validate critical applications with ASTM D471 immersion testing.
Is Sodium Hydroxide compatible with NBR (nitrile) O-rings?
NBR is rated B for Sodium Hydroxide: good — suitable for most applications. NBR is the lowest-cost elastomer, so when it earns an A or B rating it is usually the economical default; when it rates C or D, do not substitute it for a higher-rated material to save cost.
Can I use PTFE O-rings with Sodium Hydroxide?
PTFE is rated A for Sodium Hydroxide: excellent — recommended for continuous service. Remember that PTFE has no elastic memory — in demanding service it needs spring energization or an elastomer core (FEP/PFA encapsulation) to maintain sealing force.
What is the best O-ring material for Sodium Hydroxide?
EPDM, PTFE, FFKM are rated A (excellent) for Sodium Hydroxide in our compatibility data and are the recommended starting point for material selection. Final selection should also account for operating temperature, pressure and whether the seal is static or dynamic.
Can I use EPDM O-rings with Sodium Hydroxide?
EPDM is rated A for Sodium Hydroxide: excellent — recommended for continuous service. Always confirm the specific fluid concentration and temperature before specifying EPDM for this service.
Need O-Rings for Sodium Hydroxide Service?
Send us your fluid, concentration and temperature — our engineers will confirm the right compound. MOQ 1 piece.