Chromic Acid (20%) vs Buna-N Compatibility
Verified chemical resistance rating (Incompatible — Immediate Failure Risk), thermal boundary limits (Not recommended at any temperature or concentration), and material specification guide for Buna-N exposed to Chromic Acid (20%) in Strong Oxidizing / Mineral Acid service.
Chromic Acid (20%) vs Buna-N: D-Severe Effect
Exposing Buna-N to Chromic Acid (20%) (Formula: H2CrO4 / CrO3 (20% aq.), CAS: 7738-94-5) carries an official rating of D-Severe Effect (Incompatible — Immediate Failure Risk). Maximum recommended thermal operating limit: Not recommended at any temperature or concentration. Best Grade A alternative materials for continuous or high-temperature service: Viton, PTFE, PVDF.
Technical Specifications and Operating Parameters
| Chemical Medium | Chromic Acid (20%) |
|---|---|
| Chemical Formula | H2CrO4 / CrO3 (20% aq.) |
| CAS Registry Number | 7738-94-5 |
| Chemical Functional Class | Strong Oxidizing / Mineral Acid |
| Wetted Material | Buna-N |
| Official Resistance Rating | D-Severe Effect (Grade D) |
| Engineering Service Verdict | Incompatible — Immediate Failure Risk |
| Max Temp and Concentration Limit | Not recommended at any temperature or concentration |
| Best Grade A Alternatives | Viton, PTFE, PVDF |
| Backtest and Audit Verification | Verified against Cole-Parmer, ISM, Graco & CP Lab Safety industrial chemical resistance charts. |
Chromic Acid (20%) Cross-Material Comparison Matrix (9 Materials)
Direct benchmark ratings across all 9 reference industrial materials for Chromic Acid (20%):
| Material Name | Compatibility Rating | Service Verdict | Temperature Limit | Datasheet |
|---|---|---|---|---|
| Buna-N | D-Severe Effect | Incompatible — Immediate Failure Risk | Not recommended at any temperature or concentration | Report |
| EPDM | C-Fair | Caution: Limited / Intermittent Service Only | Ambient intermittent contact only; do not pressurize | Report |
| HDPE | B-Good | Acceptable with Operating Controls | Ambient service (72°F / 22°C) preferred; monitor wear in continuous service | Report |
| Polypropylene | C1-Fair | Caution: Short-Term or Emergency Use Only | Short-term exposure only; avoid continuous pressurized service | Report |
| PTFE | A-Excellent | Safe for Continuous Industrial Service | Ambient to elevated operating temperatures within standard material limits | Report |
| PVC | B-Good | Acceptable with Operating Controls | Ambient service (72°F / 22°C) preferred; monitor wear in continuous service | Report |
| PVDF | A1-Excellent | Safe for Continuous Industrial Service | Up to 120°F (49°C) verified; up to material thermal limit in non-pressurized service | Report |
| Stainless Steel | B1-Good | Acceptable with Routine Inspection | Up to 120°F (49°C) with minor absorption/corrosion allowance | Report |
| Viton | A-Excellent | Safe for Continuous Industrial Service | Ambient to elevated operating temperatures within standard material limits | Report |
Chemical and Material Interaction Analysis
Engineering Compatibility Verdict
Chromic Acid (20%) vs Buna-N: D – Severe Effect (Do Not Use)
Summary Verdict: Buna-N (Nitrile / NBR Elastomer) is rated D-Severe Effect (Incompatible — Immediate Failure Risk) when exposed to Chromic Acid (20%) (Formula: H2CrO4 / CrO3 (20% aq.), CAS: 7738-94-5). PROHIBITED for wetted service. Immediately substitute with an A-rated material shown in the cross-material comparison table below.
Quick Engineering Specifications
| Chemical Media | Chromic Acid (20%) |
|---|---|
| Chemical Formula | H2CrO4 / CrO3 (20% aq.) |
| CAS Registry Number | 7738-94-5 |
| Chemical Classification | Strong Oxidizing / Mineral Acid |
| Wetted Material | Buna-N (Nitrile / NBR Elastomer) (Acrylonitrile-Butadiene Copolymer Elastomer) |
| Official Resistance Rating | D – Severe Effect (Do Not Use) (Grade D) |
| Recommended Temperature Window | Not recommended at any temperature or concentration (Material limit: -40°F to 250°F (-40°C to 121°C)) |
| Top Grade-A Alternatives | Viton, PTFE, PVDF |
| Data Verification Status | Verified against Cole-Parmer, ISM, Graco & CP Lab Safety industrial chemical resistance charts. |
Chemical & Material Interaction Analysis
Chromic Acid (20%) is classified as a strong oxidizing / mineral acid (corrosive proton attack combined with strong oxidative potential). Used in chemical synthesis, metal pickling, pH neutralization, and industrial etching. When selecting wetted components for Buna-N, engineers must account for both concentration-dependent chemical attack and thermal stress:
- Reaction & Failure Mechanism: Causes rapid, catastrophic material failure—including severe dissolution, stress cracking, extreme volumetric blowout (>25% swell), or rapid pitting corrosion (>50 mpy).
- Material Profile (Buna-N): Workhorse elastomer for petroleum-based hydraulic oils, motor oils, diesel, gasoline, aliphatic hydrocarbons (hexane, heptane), water, and salt brines. However, poor resistance to ozone/weathering and rapidly destroyed by ketones, esters, chlorinated hydrocarbons, aromatic solvents, and strong oxidizing acids.
- Application Scope: Common wetted components include hydraulic O-rings, fuel transfer hoses, rotary shaft seals, oil gaskets, and general-purpose industrial pump elastomers.
Cross-Material Compatibility Comparison for Chromic Acid (20%)
To help you select the longest-lasting piping, valve lining, or O-ring seal for Chromic Acid (20%), the table below compares Buna-N against 8 other common industrial engineering materials:
| Wetted Material | Compatibility Rating | Service Recommendation | Material Temp Range |
|---|---|---|---|
| Polypropylene (PP Homopolymer & Copolymer) | C1-Fair | Caution: Short-Term or Emergency Use Only | 32°F to 180°F (0°C to 82°C) |
| 316 / 304 Austenitic Stainless Steel | B1-Good | Acceptable with Routine Inspection | -325°F to 800°F (-198°C to 426°C) |
| Viton® (FKM Fluoroelastomer) | A-Excellent | Safe for Continuous Industrial Service | -15°F to 400°F (-26°C to 204°C) |
| PTFE (Teflon® / Polytetrafluoroethylene) | A-Excellent | Safe for Continuous Industrial Service | -328°F to 500°F (-200°C to 260°C) |
| EPDM (Ethylene Propylene Diene Monomer) | C-Fair | Caution: Limited / Intermittent Service Only | -60°F to 300°F (-51°C to 149°C) |
| PVC Type I (Unplasticized Polyvinyl Chloride / uPVC) | B-Good | Acceptable with Operating Controls | 32°F to 140°F (0°C to 60°C) |
| PVDF (Kynar® / Polyvinylidene Fluoride) | A1-Excellent | Safe for Continuous Industrial Service | -40°F to 280°F (-40°C to 138°C) |
| Buna-N (Nitrile / NBR Elastomer) (Current Page) | D-Severe Effect | Incompatible — Immediate Failure Risk | -40°F to 250°F (-40°C to 121°C) |
| HDPE (High-Density Polyethylene) | B-Good | Acceptable with Operating Controls | -60°F to 140°F (-51°C to 60°C) |
Frequently Asked Questions (FAQ)
Is Buna-N compatible with Chromic Acid (20%)?
Buna-N is rated D-Severe Effect (Incompatible — Immediate Failure Risk) with Chromic Acid (20%) (Formula: H2CrO4 / CrO3 (20% aq.), CAS: 7738-94-5). Causes rapid, catastrophic material failure—including severe dissolution, stress cracking, extreme volumetric blowout (>25% swell), or rapid pitting corrosion (>50 mpy). PROHIBITED for wetted service. Immediately substitute with an A-rated material shown in the cross-material comparison table below.
What is the best alternative material for handling Chromic Acid (20%)?
If Buna-N does not meet your temperature or pressure requirements for Chromic Acid (20%), the highest-rated Grade A alternatives are Viton, PTFE, PVDF. Always verify O-ring elastomers and metallic fasteners separately before full-scale deployment.
Technical Engineering FAQs: Chromic Acid (20%) vs Buna-N
Click any question below for chemical failure-mode specifics, thermal derating limits, and material selection rules: