2% Nitric AcidNital 2%
2% Nital
General Purpose
Composition
2% Nitric Acid in Ethanol
2%
Method
Immersion
Time
5–30 s
Alternative Names
Tags
Reveals
Ferrite grain boundaries; pearlite (darkened by cementite-ferrite interface attack); bainite; mild contrast on martensite
Typical Results
The workhorse etchant for carbon and low-alloy steels. Darkens pearlite, leaves ferrite light, and reveals ferrite grain boundaries in annealed and normalized structures. Mild attack, appropriate as the first-try etchant on unknown steel.
Application Method
Method:Immersion
Typical Time:5–30 s
Preparation Notes
Mix 2 ml concentrated nitric acid (HNO₃) with 98 ml ethanol (95% or absolute). Add acid to ethanol slowly with stirring. Store in glass bottle.
Application Notes
Immerse the polished surface 5–30 s at room temperature. Swab gently if attack is uneven. Rinse with ethanol, then water; air-dry.
Troubleshooting
Over-etch flattens ferrite contrast and darkens the whole surface; repolish lightly with 1 µm diamond and re-etch shorter. Under-etch on bainite or fine pearlite; step up to 3% Nital or extend to 30 s.
Storage Notes
Tightly capped amber glass at room temperature; vent occasionally (NOx evolution). Stable 3–6 months.
Alternative Etchants
- 3% Nital
- 4% Picral
- Klemm's Reagent
Similar Etchants
- 3% Nital
- 5% Nital