Weck's Reagent
Weck's Etch
Material Specific
Composition
100ml Hâ‚‚O, 4g KMnOâ‚„, 4g NaOH
4% each
Method
Immersion (warm)
Time
30–120 s at 60–80 °C
Alternative Names
Tags
Reveals
Color-tinted grains in Al, Mg, and Zn alloys (orientation-dependent under polarized light); second-phase particles (Al-Si eutectic, Mg17Al12); grain structure in castings
Typical Results
Weck's color etchant (KMnO4 + NaOH in water) for aluminum, magnesium, and zinc alloys. Particularly effective on cast Al-Si alloys (319, 356, 380) and Mg-Al castings (AZ91, AM60), distinguishing alpha-Mg from Mg17Al12. NOT a stainless etchant; use Beraha's or Klemm's for steels.
Application Method
Method:Immersion (warm)
Typical Time:30–120 s at 60–80 °C
Preparation Notes
Dissolve 4g KMnO₄ and 4g NaOH in 100ml water. Heat to 60°C.
Application Notes
Heat solution to 60–80 °C. Immerse polished sample 30–120 s. Rinse with water then ethanol; air-dry only (compressed air re-deposits residue).
Troubleshooting
View under polarized light with a sensitive tint plate to see the orientation color contrast. Over-etch produces uniform dark; repolish and re-etch shorter. KMnO4 stains skin and bench; handle in tray.
Storage Notes
Amber glass at room temperature. Prepare fresh weekly; KMnO4 degrades, especially after heating.
Alternative Etchants
- Barker's Reagent (Electrolytic) for Al
- Klemm's Reagent for Mg, Zn
Similar Etchants
- Klemm's Reagent
- Barker's Reagent (Electrolytic)