Rating
| Concentration | 20 °C | 50 °C | Remark |
|---|---|---|---|
| 1-5 % | A | A | |
| 20 % | A | C | |
| 30 % | A | C | |
| 85 % | B | D |
Material comparison at 20 °C
Resistance overview
The resistance of SS 304 to Phosphoric Acid is concentration-dependent. Across the 4 tested concentrations (1-5 %, 20 %, 30 %, 85 %), 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
Phosphoric Acid is commonly encountered in chemical processing and surface cleaning. SS 304 (Stainless steel 1.4301 (AISI 304)) is a metal typically used for vessels, heat exchangers, fittings and structural components. Because Phosphoric Acid is classified as corrosive, the choice of containment material is especially critical to prevent leaks, equipment damage, and safety hazards.
Practical recommendation
SS 304 is suitable for use with Phosphoric Acid under normal conditions, but some minor effects on the material are expected over time. Periodic monitoring for swelling, softening, or weight change is recommended, especially for long-service components. Avoid prolonged exposure at elevated temperatures, as the resistance decreases further at 50 °C. For safety-critical or long-life applications, consider HDPE, LDPE, Polycarbonate instead, which are rated A for this chemical.
Did you know?
Chemical resistance testing according to DIN and ISO standards typically evaluates weight change, dimensional change, and retention of tensile strength after immersion.
Materials rated A or B at 20 °C
Based on the row for 85 %, 20 °C.
- Thermoplastics
- HDPE A, PP A, PVC Rigid A, LDPE A, Polycarbonate A, PVC Flexible A, Polystyrene A, Polysulfone A, PMP A, SAN A
- Fluoropolymers
- PTFE A, PVDF A, FEP A, ECTFE/ETFE A
- Elastomers
- Viton (FPM) A
- Metals
- SS 316 A
About SS 304
Stainless steel 304 (1.4301) resists oxidising acids and most organic chemicals. Chlorides cause pitting and stress-corrosion cracking.
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.