Copper Etchant No. 2
Copper No. 2
Material Specific
Composition
Hydrogen chloride 10–15%, Ferric chloride 5–10%
PACE product, by weight
Method
Swab or immersion
Time
10–60 s
Alternative Names
Tags
Reveals
Grain boundaries, alpha–beta phases in brass, second-phase particles in age-hardened Cu alloys (CuBe, CuCr, CuZr)
Typical Results
Acidic ferric-chloride etchant: FeCl3 oxidizes copper while HCl strips the chloride layer. Standard for OFHC copper, brass, bronze, and beryllium copper. Slightly more aggressive than NH4OH + H2O2; longer shelf life. (This is the only PACE product containing ferric chloride; the previous standalone "Ferric Chloride" SKU was a duplicate and has been removed.)
Application Method
Method:Swab or immersion
Typical Time:10–60 s
Preparation Notes
PACE Copper No. 2 is supplied ready-to-use. Composition (by weight):
| Ingredient | CAS No. | % | Hazardous |
|---|---|---|---|
| Hydrogen chloride | 7647-01-0 | 10–15% | Yes |
| Ferric chloride | 7705-08-0 | 5–10% | Yes |
| Water | 7732-18-5 | 75–85% | No |
Application Notes
Swab or immerse 10–60 s at room temperature. Rinse promptly with water; delayed rinse leaves iron staining. Follow with ethanol; passivate with Cu-Pass-Sol.
Troubleshooting
Iron staining if rinse delayed: flush immediately. Aged CuBe (HT-temper) needs the longer end of the time window. Be-Cu dust is toxic; handle hardened CuBe with care.
Storage Notes
Amber glass at room temperature. Stable many months; color darkens with age but solution remains active.
Alternative Etchants
- Copper No. 1
- Ammonium Persulfate
- Ammonium Hydroxide + H2O2
Similar Etchants
- Ammonium Persulfate