Differences between ASTM A262 Practice C and ASTM A262 Practice E for intergranular corrosion IGC testing
| Parameter | ASTM A262 Practice C (Nitric Acid Test) | ASTM A262 Practice E (Copper-Copper Sulfate-Sulfuric Acid Test) |
|---|---|---|
| Test Medium | 65% nitric acid (boiling) | 16% sulfuric acid + 6% copper sulfate + copper chips (boiling) |
| Test Duration | 5 cycles (48 hours each, total 240 hours) | 15 hours continuous boiling min |
| Targeted Materials | Austenitic stainless steels (e.g., 304, 316) | Austenitic & duplex stainless steel (e.g., 304L, 316L, 2205) |
| Detection Focus | IGC + end-grain attack (σ-phase sensitivity) | IGC (especially in welded/sensitized materials) |
| Evaluation Method | Weight loss (pass if ≤0.05 g/m²·h) | Bend test (failure if cracks appear) or metallographic examination |
| Primary Application | Evaluates resistance to nitric acid | Assesses IGC susceptibility in welded/sensitized structures |
| Test Severity | Highly aggressive (prolonged exposure) | Moderate (shorter exposure, focused on weld zones) |
| Key Standard Ref. | ASTM A262 Practice C | ASTM A262 Practice E |
Key Differences Summary:
- Medium & Mechanism:
- Practice C: Uses nitric acid to detect σ-phase and general IGC.
- Practice E: Uses sulfuric acid + CuSO₄ to accelerate IGC in sensitized regions.
- Duration:
- Practice C: Long-term (240 hours) for chronic corrosion resistance.
- Practice E: Short-term (15 hours) for rapid screening.
- Output:
- Practice C: Quantitative (weight loss).
- Practice E: Qualitative (bend test cracks).
- Material Scope:
- Practice C: Standard austenitic grades (304/316).
- Practice E: Includes low-carbon (304L) and duplex steels (2205).
Typical Use Cases:
- Practice C: Chemical tanks exposed to nitric acid.
- Practice E: Welded pipelines or heat-treated components.
For exact procedural details (e.g., specimen dimensions, solution prep), refer to ASTM A262.
