Potassium Dichromate
Dichromate Etchant
Material Specific
Composition
Potassium dichromate 2–5%, Sulfuric acid 5–10%, Sodium chloride 2–10%
PACE product, by weight
Method
Immersion or swab
Time
5–30 s
Alternative Names
Tags
Reveals
Grain boundaries; alpha–beta phases in brass; second-phase contrast in bronze
Typical Results
Acidified potassium dichromate with NaCl. Chromate-sulfuric-chloride etchant for copper alloys, brass, and bronze. The NaCl + dichromate combination is more selective than ammonia-peroxide on some Cu-Zn brasses with phase separation. CARCINOGENIC (Cr(VI)): full PPE and fume hood required.
Application Method
Method:Immersion or swab
Typical Time:5–30 s
Preparation Notes
PACE Dichromate Etchant is supplied ready-to-use. Composition (by weight):
| Ingredient | CAS No. | % | Hazardous |
|---|---|---|---|
| Potassium dichromate | 7778-50-9 | 2–5% | Yes |
| Sulfuric acid | 7664-93-9 | 5–10% | Yes |
| Sodium chloride | 7647-14-5 | 2–10% | Yes |
| Water | 7732-18-5 | 80–90% | No |
Application Notes
Immerse or swab 5–30 s at room temperature. Rinse with water then ethanol; passivate with Cu-Pass-Sol if standing time before imaging.
Troubleshooting
Cr(VI) is a known human carcinogen; full containment required. Dispose of solution and rinsate as regulated waste. Solution darkens with use but remains active for months.
Storage Notes
Glass bottle with tight cap; secondary containment. Hazardous-waste protocol on disposal. Stable many months.
Alternative Etchants
- Ammonium Persulfate
- Copper No. 2
- Ammonium Hydroxide + H2O2
Similar Etchants
- Chromate-based Cu etchants