The chart says "resistant". The material was approved. Yet after a few months a seal swells, or a line starts to weep at a flange. With aggressive media, that is not a minor issue: it means leaks, downtime and a contaminated process. ECTFE has a strong reputation for resisting acids, alkalis and oxidizing agents. But ECTFE chemical compatibility is never absolute. This article explains what ECTFE resists, where its limits are and how to read a chemical resistance chart correctly, so you can run a first suitability check yourself.
Every rating in a chart is valid under specific test conditions. In a real process, more factors come into play:
Look at one line in a chart and you miss this context. The result: premature failure, unplanned replacement or product contamination. In high-purity or toxic service, those costs add up quickly.
ECTFE is an alternating copolymer of ethylene and chlorotrifluoroethylene, also known under the brand name Halar®. According to the Polyfluor datasheet, it offers high resistance to acids and oxidizing agents, very low permeation and good moisture resistance.
That makes ECTFE a logical candidate in the petrochemical industry, in water treatment and in any process involving chlorine or hypochlorite. The Polyfluor chart for ECTFE gives ratings at 20 °C, 60 °C and 100 °C. Here is what it shows for typical media:
|
Medium |
Rating (20 / 60 / 100 °C) |
Point of attention |
|
Sulfuric acid (<50 %, 70 %, 95 %, fuming) |
R / R / R |
Rated resistant across all listed concentrations |
|
Hydrochloric acid 10 % |
R / R / R |
– |
|
Hydrochloric acid, concentrated |
R / R / ND |
No data at 100 °C |
|
Nitric acid 50 % and 90 % |
R / R / NR |
Not recommended at 100 °C |
|
Caustic soda and potash |
R / R / R |
Key difference from PVDF |
|
Chlorine (dry/wet), sodium hypochlorite 12–14 % |
R / R / R |
Typical ECTFE application |
|
Monoethanolamine |
R / R / NR |
Amines at elevated temperature need checking |
|
Dry fluorine |
R / R / NR |
Not recommended at 100 °C |
R = resistant, NR = not recommended, ND = no data. Source: Polyfluor chemical resistance chart for ECTFE.
Temperature is the second limit. ECTFE can be used continuously from −75 °C to +150 °C and briefly up to 180 °C. The chart stops at 100 °C, so anything above that needs a separate assessment.
Permeation deserves as much attention as chemical attack. A medium can leave the polymer intact and still migrate through it slowly. That leads to emissions, corrosion of surrounding metal parts or contamination of a high-purity fluid. ECTFE's very low permeation is one of the main reasons engineers choose it.
Weighing ECTFE against PVDF? The pH range is often decisive: ECTFE is rated resistant to strong alkalis such as caustic soda up to 100 °C, where PVDF is known to be sensitive. For a broader comparison with ETFE and PTFE, see our article on ECTFE vs ETFE.
A chemical resistance chart gives a rating per medium, usually in classes such as resistant (R), limited resistance (LR), not recommended (NR) and no data (ND). Three points decide how useful that rating is:
Extrapolation is risky. "R at 60 °C" does not automatically mean "R at 120 °C". When in doubt, use the most severe condition your process can reach.
List every medium the part will see, with concentration and temperature. Include peaks such as start-up, cleaning and upset conditions. Those moments often determine service life.
Look up each medium in the ECTFE chemical resistance chart. Then compare the result with the ECTFE datasheet (PDF) for temperature limits and mechanical properties.
Ask what happens if the medium passes through the wall. With gases, vapors and high-purity fluids, permeation is often the real risk.
Add cleaning and disinfection chemicals to the assessment. A line that only sees acid in production may be exposed to caustic or an oxidizer during cleaning.
Is your medium missing from the chart, rated ND, or are your conditions outside the tested range? Have the application reviewed. Sometimes a practical test is the only reliable route.
Consider a process line in the pharmaceutical industry or the semiconductor industry. In production it carries an acidic medium. During the CIP cycle, a caustic rinse follows, then an oxidizing cleaning agent.
For many polymers, that alternation is the problem: compatible with the acid, but not the caustic, or vice versa. ECTFE is rated resistant across this whole spectrum, and its low permeation keeps the medium clean.
The question still to verify: what is the maximum temperature during cleaning, and how long does that phase last?
ECTFE chemical compatibility is broad: acids, strong alkalis and oxidizers rarely cause problems, and permeation is very low. The limits lie with specific media at elevated temperature, such as concentrated nitric acid and amines at 100 °C, and with the service temperature of the material itself. A chart is a starting point, not a final verdict. Factor in concentration, temperature, permeation and cleaning cycles, and you make a reliable choice.
Not sure whether ECTFE is compatible with your medium? Our specialists are happy to review your application with you. Contact us.
Yes. The Polyfluor chart rates ECTFE as resistant to sulfuric acid below 50 %, at 70 %, at 95 % and fuming, at 20, 60 and 100 °C. Above 100 °C, have your conditions assessed separately.
ECTFE is rated resistant to 10 % hydrochloric acid up to 100 °C. For concentrated HCl the rating is resistant up to 60 °C; there is no data at 100 °C. At higher temperatures, also consider HCl vapor permeation.
Halar® is a brand name for ECTFE. The chart rates ECTFE as resistant to sodium hypochlorite (12–14 %) and to wet and dry chlorine up to 100 °C. That is why ECTFE is widely used for chlorine and hypochlorite dosing and storage.
At 100 °C the chart lists ECTFE as not recommended for nitric acid at 50 % and 90 %, monoethanolamine, dry fluorine, amyl acetate, ethylene glycol and picric acid. Like other fluoropolymers, it is also unsuitable for molten alkali metals.
In strongly alkaline media it usually is: ECTFE is rated resistant to caustic soda up to 100 °C, while PVDF is sensitive to high pH. ECTFE also has a higher service temperature. For many acids and moderately aggressive media, PVDF can be a suitable and more economical choice.