Murakami's Etchant
Murakami's Reagent
Specialty
Composition
Potassium ferricyanide 10–30%, Potassium hydroxide 10–30%
PACE product, by weight
Method
Immersion (cold or boiling)
Time
30–60 s cold (carbide work) / 2–6 min boiling (sensitization, A262 Practice E)
Alternative Names
Tags
Reveals
COLD: eta phase and Co binder distribution in WC-Co cemented carbides; sigma phase in stainless. BOILING: Cr-depleted grain boundaries in sensitized austenitic stainless (ASTM A262 Practice E / Strauss).
Typical Results
Dual-use etchant. (1) Cold at room temperature: stains binder cobalt and eta phase in WC-Co tungsten carbide; reveals sigma in some stainless. (2) Boiling (~100 °C, 2–6 min): the Strauss sensitization test for austenitic stainless steels per ASTM A262 Practice E.
Application Method
Method:Immersion (cold or boiling)
Typical Time:30–60 s cold (carbide work) / 2–6 min boiling (sensitization, A262 Practice E)
Preparation Notes
PACE Murakami's Reagent is supplied ready-to-use. Composition (by weight):
| Ingredient | CAS No. | % | Hazardous |
|---|---|---|---|
| Potassium ferricyanide | 13746-66-2 | 10–30% | Yes |
| Potassium hydroxide | 1310-58-3 | 10–30% | Yes |
| Water | 7732-18-5 | 70–85% | No |
Application Notes
For WC work: immerse cold 30–60 s; rinse with water. For sensitization: boil 2–6 min per A262 Practice E (use a reflux setup); cool, rinse, examine.
Troubleshooting
K3Fe(CN)6 + acid evolves HCN; keep solution alkaline at all times. Hot solution can boil over; use a fume hood and reflux. Cool solution before disposal.
Storage Notes
Amber glass at room temperature. Stable several months sealed. Discard if greenish-blue (Fe(II) formation).
Alternative Etchants
- 10% Oxalic Acid (Electrolytic), A262 Practice A
- Glyceregia, A262 Practice C
- Marble's Reagent (WC)
Similar Etchants
- Sensitization-test family (A262 A/B/C/E/F)