Vilella's Etchant
Vilella's Reagent
Specialty
Composition
1g Picric Acid, 5ml HCl, 100ml Ethanol
Mixed
Method
Immersion
Time
10–60 s
Alternative Names
Tags
Reveals
Prior austenite grain boundaries; tempered martensite needle structure; carbides (M23C6, MC) in hardened tool and HSS; segregation in PH stainless
Typical Results
Vilella's reagent (1 g picric + 5 mL HCl + 100 mL ethanol) is the standard etchant for martensitic stainless steels (410, 420, 440C), precipitation-hardening stainless (17-4 PH, 15-5 PH), and hardened tool/high-speed steels (M2, T1, D2, A2). Reveals prior austenite grain boundaries cleanly.
Application Method
Method:Immersion
Typical Time:10–60 s
Preparation Notes
Dissolve 1g picric acid in 5ml HCl, then add 100ml ethanol. CAUTION: Picric acid is explosive when dry.
Application Notes
Immerse the polished surface 10–60 s at room temperature. Swab if attack is uneven. Rinse with ethanol then water; air-dry.
Troubleshooting
PICRIC ACID: never let the solution dry. Dry picric crystals are shock-sensitive explosives. Keep at least 10% water above any solid at all times.
Storage Notes
Amber glass; keep wet at all times. Inspect monthly and add water if level drops. EXPLOSIVE WHEN DRY. Stable months when wet.
Alternative Etchants
- Adler's Etchant (PH stainless)
- Carpenter's (tool steel)
- Winsteard's Reagent (with wetting agent)
Similar Etchants
- Winsteard's Reagent