Hydrochloric Acid (HCl)
Real material compatibility from 10% through 38% concentration — where common elastomers fail near room temperature, and where even fluoropolymers hit a real ceiling.
Hydrochloric acid is aggressive to commodity plastics even at relatively low concentrations — HDPE and PP are only conditional (never fully resistant) even at 10%. Fluoropolymers (PVDF, ECTFE, PTFE, FEP, PFA) are the reliable material choice across the tested range, but even they have a real ceiling: at 38% near-azeotropic concentration, ECTFE itself drops to failing by 212°F. Common elastomers (FKM, EPDM) fail near room temperature by 35% concentration — a real, low-temperature failure point.
What Survives, By Concentration
10%
HDPE and PP are both only conditional through 176°F — never fully resistant even at this relatively low concentration. PVDF, ECTFE, PTFE, FEP, and PFA are fully resistant through 212-248°F. NBR fails even at 68°F.
≤25%
PVC/CPVC resistant through 140-176°F. FKM good through 140°F, conditional at 176°F, fails by 212°F. EPDM good through 140°F, fails by 176°F.
35%
PP flips from conditional to failing by 176-212°F. FKM and EPDM — both common elastomers — fail near room temperature: FKM conditional at 68°F, failing by 104°F; EPDM the same pattern.
38% (near-azeotropic)
HDPE fails even at 68°F. PP is conditional-to-failing across the range. Even ECTFE — normally a strong performer — drops to failing by 212°F at this concentration, a real ceiling worth confirming.
Source: combined chemical resistance chart, 858 real data rows. Confirm current ratings with the manufacturer before final specification.
HCl Fume & Scrubbing
Liquid-phase material compatibility (above) is a separate engineering question from vapor-phase HCl fume handling. See the real HCl Fume Scrubber case study for documented equipment specified to capture and neutralize HCl vapor, rather than contain the liquid acid.
Frequently Asked Questions
Is HDPE piping suitable for hydrochloric acid service?
Not reliably — even at a relatively low 10% concentration, HDPE and PP are only conditional (not fully resistant) through 176°F. Fluoropolymers (PVDF, ECTFE, PTFE, FEP, PFA) are the reliable choice across the concentration range tested, especially as concentration rises toward 35-38%.
At what HCl concentration do common elastomers fail?
By 35% concentration, both FKM and EPDM — the two most common elastomer seal choices — fail near room temperature (FKM conditional at 68°F, failing by 104°F; EPDM the same pattern). This is a real, low-temperature failure point that catches specifiers who assume elastomer failure only happens at elevated temperature.
Does even fluoropolymer piping have a real ceiling for HCl?
Yes — at 38% (near-azeotropic) concentration, even ECTFE (normally resistant through 212-248°F at lower concentrations) drops to failing by 212°F. This is a real, concentration-driven ceiling, not just a temperature limit, and it's worth confirming specifically at the highest concentration your application actually runs.
What real-world case involves hydrochloric acid fume handling?
A documented HCl fume scrubber case addresses the vapor-phase handling side of this chemistry — see the related case study for real equipment specified for HCl fume capture, distinct from the liquid-phase material compatibility covered here.
Confirm your exact concentration before you specify
Send LibertyCES your real HCl concentration and temperature — we'll confirm the right material, not the generic answer.
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