Rating
| Concentration | 20 °C | 50 °C | Remark |
|---|---|---|---|
| 1 % | A | A | |
| 30 % | C* | – | |
| 45 % | B | D | |
| 50 % | C | D | |
| 60 % | C | D | |
| concentrated | D | D |
* estimated rating, given in the source without a temperature
Material comparison at 20 °C
Resistance overview
The resistance of Viton (FPM) to Sodium Hydroxide (Caustic Soda) is concentration-dependent. Across the 6 tested concentrations (1 %, 30 %, 45 %, 50 %, 60 %, concentrated), the 20 °C rating ranges from A at lower concentrations to D at higher ones. This means engineers must verify which concentration their process actually involves before relying on a single rating. However, at 50 °C the resistance rating drops, indicating that temperature must be factored into the design. For heated applications, additional testing under actual service conditions is strongly recommended.
Application context
Sodium Hydroxide (Caustic Soda) is commonly encountered in cleaning and sanitation and pulp and paper. Viton (FPM) (Fluoroelastomer (FKM/FPM)) is an elastomer typically used for seals, O-rings, hoses and flexible connections. Because Sodium Hydroxide (Caustic Soda) is classified as corrosive, the choice of containment material is especially critical to prevent leaks, equipment damage, and safety hazards.
Practical recommendation
Viton (FPM) has limited resistance to Sodium Hydroxide (Caustic Soda) and should only be used for short-term or intermittent contact at ambient temperature. The C rating means the material undergoes noticeable changes — swelling, loss of strength, or surface degradation — that make it unsuitable for permanent installations. For prolonged or continuous exposure, HDPE, LDPE, Nylon (PA) offer significantly better resistance and are rated A.
Did you know?
When choosing between elastomers for Sodium Hydroxide (Caustic Soda) service, engineers consider not just the resistance rating but also factors such as permeation rate, creep resistance, and weldability.
Materials rated A or B at 20 °C
Based on the row for 60 %, 20 °C.
- Thermoplastics
- HDPE A, PP A, LDPE A, Nylon (PA) A, Polystyrene A, Polysulfone A, PMP A
- Fluoropolymers
- PTFE A
- Elastomers
- EPDM A, NBR B
- Metals
- SS 316 A, SS 304 A
About Viton (FPM)
Fluoroelastomer (Viton, FKM/FPM) resists fuels, oils and many acids. Ketones, esters, amines and hot water or steam attack it.
Rating scale
- A very good resistance
- B good resistance
- C limited resistance
- D not resistant
- – no data
- K no general statement possible
A rating marked * is an estimate in the source, not a test result. An estimate is given as one value without a temperature.
About this data
The ratings come from the chemical resistance list published by Bürkle GmbH, which compiled them from raw-material manufacturers’ data. They describe laboratory tests on the raw material at 20 °C and 50 °C.
A finished part also sees pressure, mechanical stress, welds and mixtures that a laboratory test does not. Treat the rating as a first filter and test under your own conditions before relying on it.