5% Nitric AcidNital 5%
5% Nital
General Purpose
Composition
5% Nitric Acid in Ethanol
5%
Method
Immersion
Time
3–15 s
Alternative Names
Tags
Reveals
Prior austenite grain boundaries in tempered martensite; tempered martensite needle structure; fine bainite; carbides at boundaries
Typical Results
Used for prior-austenite grain boundary revealing in tempered martensitic alloy steels (4140, 4340, 8620, AISI O1). Over-etches normalized low-carbon steel; use 2% or 3% Nital there. Below 5% if the prior austenite grain boundaries are very fine.
Application Method
Method:Immersion
Typical Time:3–15 s
Preparation Notes
Mix 5 ml concentrated nitric acid with 95 ml ethanol. Add acid slowly to ethanol.
Application Notes
Immerse 3–15 s at room temperature. Start short; 5% is aggressive on softer steels. Rinse with ethanol then water; air-dry.
Troubleshooting
Whole-surface darkening: too long; drop to 3% or shorten dwell. Failed PAGB reveal: re-temper at lower temperature, or use a picric-acid-based PAGB etch.
Storage Notes
Tightly capped amber glass. Stable 3–6 months.
Alternative Etchants
- 3% Nital
- Vilella's Reagent
- 4% Picral
Similar Etchants
- 3% Nital
- 8% Nital