Marble's Etchant
Marble's Reagent
Material Specific
Composition
Hydrogen chloride 10–20%, Cupric sulfate 2–10%
PACE product, by weight
Method
Swab
Time
5–60 s
Alternative Names
Tags
Reveals
Grain boundaries; primary carbides (MC, M23C6); secondary phases in Ni-base superalloys, austenitic stainless, and Co-base alloys
Typical Results
Classical Marble's reagent: HCl + CuSO4 + water. Workhorse etchant for nickel-base superalloys (Inconel 600/625/718), austenitic stainless, and cobalt-base alloys (Stellite, L-605). Reveals grain structure and primary carbide network. Often paired with an electrolytic gamma-prime etch for full superalloy characterization.
Application Method
Method:Swab
Typical Time:5–60 s
Preparation Notes
PACE Marble's Reagent is supplied ready-to-use. Composition (by weight):
| Ingredient | CAS No. | % | Hazardous |
|---|---|---|---|
| Hydrogen chloride | 7647-01-0 | 10–20% | Yes |
| Cupric sulfate | 7758-98-7 | 2–10% | Yes |
| Water | 7732-18-5 | 70–85% | No |
Application Notes
Swab 5–60 s at room temperature. Rinse with water then ethanol.
Troubleshooting
Copper deposit (brownish stain) if dwell too long: repolish with 0.05 µm and re-etch shorter. Solution darkens with use but remains active.
Storage Notes
Amber glass at room temperature. Stable many months.
Alternative Etchants
- Kalling's No. 2
- Glyceregia
- Inconel Etchant
Similar Etchants
- Kalling's No. 2