4% Nitric AcidNital 4%
4% Nital
General Purpose
Composition
4% Nitric Acid in Ethanol
4%
Method
Immersion
Time
5–20 s
Alternative Names
Tags
Reveals
Ferrite grain boundaries; pearlite; tempered martensite; bainite
Typical Results
Intermediate-strength nital. Use when 3% under-etches but 5% over-etches; practical for tempered martensite contrast in medium-alloy steels. 2% and 5% are the more common strengths; 4% is a fine-tuning option.
Application Method
Method:Immersion
Typical Time:5–20 s
Preparation Notes
Mix 4 ml concentrated nitric acid (HNO₃) with 96 ml ethanol. Add acid to ethanol slowly with stirring.
Application Notes
Immerse 5–20 s at room temperature. Rinse with ethanol then water; air-dry.
Troubleshooting
If contrast is similar to 3%, the 1% step did not buy useful selectivity; try a longer dwell with 3% first.
Storage Notes
Tightly capped amber glass at room temperature. Stable 3–6 months.
Alternative Etchants
- 3% Nital
- 5% Nital
Similar Etchants
- 3% Nital
- 5% Nital