Side-by-side chemical compatibility chart for Greene, Tweed Chemraz 505 and DuPont Kalrez 6375 FFKM O-rings against 18 industrial and petrochemical media. A/B/C/D rating with notes on where the two grades diverge (Chemraz preferred for amines / EO / wet Cl2 / SC1; Kalrez preferred for hot steam).
Perfluoroelastomer (FFKM) O-rings sit at the top of the chemical-compatibility ladder — the fluorinated C-C-F backbone resists solvents, acids and hot oxidisers that swell or attack FKM (Viton) and NBR. Two grades cover most industrial and petrochemical applications: Greene, Tweed Chemraz 505 (black, 75 IRHD, USP Class VI, continuous 230 °C) and DuPont Kalrez 6375 (black, 75 IRHD, continuous 275 °C). Rating: A = excellent, B = good, C = marginal, D = not recommended.
| Media | Chemraz 505 | Kalrez 6375 | Note |
|---|---|---|---|
| Aromatic hydrocarbons (toluene, xylene) | A | A | Both excellent to 260 °C. |
| Aliphatic hydrocarbons (hexane, gasoline) | A | A | Retain shape + modulus long term. |
| Crude oil / condensate | A | A | Standard spec for wellhead + downstream refining. |
| Ethylene oxide (EO) | A | B | Chemraz 505 has FDA + USP Class VI; K6375 rated but qualifies less strongly. |
| Amines (aniline, MEA, DEA) | A | B | Chemraz preferred; Kalrez shows swelling in DEA > 150 °C. |
| Concentrated sulphuric acid (98 %) | A | A | FFKM standard for hot conc. H₂SO₄. |
| Nitric acid 70 % | B | C | Chemraz outperforms Kalrez in hot conc. HNO₃; both attacked > 90 °C. |
| Hydrofluoric acid (aq) | A | A | Standard FFKM service. |
| Steam (high-pressure, 200+ °C) | B | A | Kalrez preferred; Chemraz to ~230 °C wet. |
| Ethylene glycol / hot water | A | A | Standard cooling / process service. |
| Ozone / oxidising gases | A | A | FFKM baseline resistance. |
| Ammonia (anhydrous) | A | B | Chemraz preferred; Kalrez swells > 5 % in hot anhydrous NH₃. |
| Fluorinated solvents (Freon, HFE) | A | A | Both compatible with common HFEs. |
| Semi-conductor cleans (SC1, SC2) | A | B | Chemraz qualified vs SC1 hot NH₄OH/H₂O₂; K8085 is DuPont's semi-conductor grade. |
| Hot chlorine / wet chlorine gas | A | B | Chemraz preferred for wet Cl₂ > 100 °C. |
| Sea water | A | A | Offshore + subsea service. |
| NORSOK M-710 sour service | A | A | Both hold API 6A + M-710 qualification. |
| Hot air (oxidative) 260 °C | A | A | Continuous 260 °C service. |
For general mixed-service refinery and offshore duty the two grades are functionally interchangeable — pick the one already qualified for the site. Chemraz 505 is preferred where the seal sees amines, ethylene oxide, wet chlorine or a semi-conductor clean (SC1 / SC2), and where a USP Class VI clearance is needed (pharma, food-contact). Kalrez 6375 is preferred where wet steam above 200 °C is the primary challenge, and where the seal is spec'd by DuPont OEM assemblies.