Sulfuric Acid (H₂SO₄)
Real material compatibility across the full 10%-100% concentration range — the same material choice that works at 70% often fails outright by 96-98%.
Sulfuric acid compatibility is heavily concentration-dependent, not a single material decision. Most common materials (PVC, CPVC, PP, PVDF, and standard elastomers) hold up fine through 70% concentration at moderate temperatures, but by 96-98% both FKM and EPDM — the two most common elastomer choices — fail outright even at room temperature, and by 100% (fuming/oleum range) only true fluoropolymers survive. A tank or valve validated for one concentration cannot be assumed safe at a higher one.
What Survives, By Concentration
10-70%
PVC, CPVC, PP, PVDF, ECTFE, PTFE, FKM, EPDM, FEP, PFA, and NBR are all resistant at 68°F. EPDM's temperature ceiling drops as concentration rises — good to 176°F at 10-60%, dropping to conditional at 140°F and failing by 176°F at 70%.
80%
HDPE flips from conditional to fully resistant at 68-104°F — an unusual non-monotonic behavior worth confirming at this specific concentration. EPDM good to 140°F conditional, fails by 176°F.
90-94%
EPDM drops sharply — conditional at 68-104°F, fails by 140°F. FKM conditional at 140-176°F, fails by 212°F. PP and HDPE both fail starting at 90%.
96-98%
PVC/CPVC drop to conditional at 68°F and fail by 104°F. FKM and EPDM — the two most common elastomers — both fail outright even at 68°F room temperature.
100% (fuming/oleum)
PVC, CPVC, PP, PVDF, FKM, EPDM, and NBR all fail even at 68°F. Only ECTFE, PTFE (partially, good to 104°F only), FEP, and PFA remain resistant.
Source: combined chemical resistance chart, 858 real data rows (12 materials × concentration × temperature). Confirm current ratings with the manufacturer before final specification.
Tank Material at High Concentration
Houston PolyTank's extrusion-wound polypropylene pressure vessels are rated for 98% sulfuric acid service, certified through a sustained 50 PSI / 24-hour hydrostatic test to DVS 2205 — but the concentration ladder above shows why this specific certification matters: PP itself starts failing at 90%+ concentration in general chart data, so a tank rated specifically for 98% service (not a generic "acid-resistant" claim) is the real differentiator. See the Houston PolyTank 3,000-Gal Pressure Tank guide for the full spec.
Frequently Asked Questions
What material holds up to 98% sulfuric acid?
At 96-98% concentration, PVC/CPVC are only conditional at room temperature and fail by 104°F, and both FKM and EPDM — the two most common elastomer choices — fail outright even at 68°F. Real fluoropolymers (PTFE, PVDF at lower temps, ECTFE, FEP, PFA) are the reliable choices at this concentration, and elastomer seal selection needs to move away from FKM/EPDM entirely.
Is EPDM ever acceptable for sulfuric acid service?
Only at lower concentrations and moderate temperatures — EPDM holds to 176°F at 10-60% concentration, but its ceiling drops sharply as concentration rises, failing outright by 96-98% regardless of temperature. Never assume EPDM compatibility without checking the specific concentration.
Why does 100% sulfuric acid behave differently from "saturated" sulfuric acid?
These are chemically distinct conditions. The 100% (fuming/oleum range) row shows PVC, CPVC, PP, PVDF, FKM, EPDM, and NBR all failing even at room temperature. A separate "saturated aqueous solution" condition shows HDPE, PP, PVDF, ECTFE, FEP, and PFA all fully resistant — a materially different real-world scenario from the anhydrous fuming-acid condition. Always confirm which condition your application actually represents.
Does tank material need to change at higher sulfuric acid concentrations?
Yes — this is not a single material decision across the full concentration range. A tank or piping system validated at 70% concentration cannot be assumed safe at 96-98%, where the same commodity plastics and common elastomers that worked at lower concentration begin failing even at room temperature.
Confirm your exact concentration before you specify
Send LibertyCES your real H2SO4 concentration and temperature — we'll confirm the right material, not the generic answer.
Ready to buy or need a fast answer? Call, text, or email James directly — (559) 395-5500 · [email protected].