Ammonia Resistant O-Rings

Compatibility ratings for 7 O-ring materials in Ammonia service

At a glance:A× 2B× 1C× 2D× 2— 2 of 7 materials recommended for Ammonia

Ammonia (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	C	fair — conditional use, verify with testing
FKM	D	not recommended — rapid degradation expected
EPDM	B	good — suitable for most applications
VMQ	D	not recommended — rapid degradation expected
PTFE	A	excellent — recommended for continuous service
FFKM	A	excellent — recommended for continuous service
HNBR	C	fair — conditional use, verify with testing

Why These Ratings

FKM (D) — documented weaknesses include “Amines.”
VMQ (D) — 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.

Use With Caution

Avoid

FKM (D)
VMQ (D)

Engineering note: ratings are general guidelines based on typical exposure conditions. Fluid concentration, temperature, pressure and exposure time can shift compatibility by a full grade or more. For critical service, validate the actual compound with ASTM D471 immersion testing before production use. Selecting across multiple chemicals? See the chemical-resistant O-ring selection guide for a material-first comparison.

Related Chemicals (Bases)

Frequently Asked Questions

Is Ammonia compatible with FKM (Viton) O-rings?

FKM is rated D for Ammonia: not recommended — rapid degradation expected. Ratings are general guidelines; concentration, temperature and exposure time all affect real-world compatibility, so validate critical applications with ASTM D471 immersion testing.

Is Ammonia compatible with NBR (nitrile) O-rings?

NBR is rated C for Ammonia: fair — conditional use, verify with testing. 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 Ammonia?

PTFE is rated A for Ammonia: 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 Ammonia?

PTFE, FFKM are rated A (excellent) for Ammonia 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 Ammonia?

EPDM is rated B for Ammonia: good — suitable for most applications. Always confirm the specific fluid concentration and temperature before specifying EPDM for this service.

Need O-Rings for Ammonia Service?

Send us your fluid, concentration and temperature — our engineers will confirm the right compound. MOQ 1 piece.

Request Material Recommendation Download Full Chart (PDF)