Aqua Regia

Material Specific

Composition

75ml HCl, 25ml HNO₃

Mixed

Method

Immersion

Time

30s

Alternative Names

Reveals

Grain boundaries, phases, carbides

Typical Results

Very aggressive etchant for noble metals and some stainless steels. Excellent for revealing grain structure in difficult-to-etch materials.

Color Effects

Grain boundaries dark, phases visible

Compatible Materials

Incompatible Materials

Application Method

Method:immersion

Typical Time:30 seconds

Preparation Notes

CAUTION: Extremely corrosive and produces toxic fumes. Mix 75ml concentrated HCl with 25ml concentrated HNO₃. Always add nitric acid to hydrochloric acid slowly. Prepare fresh - decomposes rapidly. Use in fume hood.

Application Notes

Immerse sample for 30-60 seconds. Swab gently if needed. Rinse immediately with copious water, then ethanol. Very aggressive - monitor closely.

Troubleshooting

Produces toxic chlorine and nitrosyl chloride fumes. Use only in fume hood with proper PPE. Prepare fresh for each use as it decomposes quickly. Very aggressive - may over-etch if left too long.

Storage Notes

Cannot be stored - prepare fresh for each use. Decomposes within hours. Store component acids separately.