Formic Acid Resistant O-Rings

Compatibility ratings for 7 O-ring materials in Formic Acid service

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

Formic Acid (Acids) 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	D	not recommended — rapid degradation expected
FKM	B	good — suitable for most applications
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

NBR (D) — documented weaknesses include “Strong acids.”
VMQ (D) — documented weaknesses include “Concentrated acids and alkalis.”
PTFE (A) — documented strengths include “Strong oxidizing acids.”
FFKM (A) — documented strengths include “Concentrated oxidising acids.”
HNBR (C) — documented weaknesses include “Strong acids.”

AcidsService: Concentration & Temperature Notes

Concentration changes everything in acid service. In our own data, sulfuric acid shifts NBR from C (dilute) to D (concentrated) and EPDM from B to C as concentration rises. Oxidizing acids (nitric, concentrated sulfuric) attack the polymer backbone chemically rather than merely swelling it, which is why PTFE and FFKM dominate this category. Temperature accelerates acid attack sharply — a rating earned at room temperature may not hold at +60°C.

Use With Caution

Avoid

NBR (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 (Acids)

Frequently Asked Questions

Is Formic Acid compatible with FKM (Viton) O-rings?

FKM is rated B for Formic Acid: good — suitable for most applications. Ratings are general guidelines; concentration, temperature and exposure time all affect real-world compatibility, so validate critical applications with ASTM D471 immersion testing.

Is Formic Acid compatible with NBR (nitrile) O-rings?

NBR is rated D for Formic Acid: not recommended — rapid degradation expected. 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 Formic Acid?

PTFE is rated A for Formic Acid: 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 Formic Acid?

PTFE, FFKM are rated A (excellent) for Formic Acid 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 Formic Acid?

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

Need O-Rings for Formic Acid Service?

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

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