Keller's Reagent

Material Specific

Buy from PACE

Composition

2ml HF, 3ml HCl, 5ml HNO₃, 190ml H₂O

Mixed

Method

Immersion

Time

8–15 s

Alternative Names

Reveals

Grain boundaries; second-phase particles (Al2Cu, Mg2Si, MgZn2); constituent particles; cold-worked vs recrystallized grains

Typical Results

Standard etchant for wrought aluminum alloys (1xxx through 7xxx). Reveals grain structure and the major intermetallic phases. May leave a Cu-rich stain on 2xxx (Cu-bearing) alloys; switch to 0.5% HF or Graff-Sargent there.

Application Method

Method:Immersion

Typical Time:8–15 s

Preparation Notes

CAUTION: HF is extremely hazardous. Mix 2ml HF, 3ml HCl, 5ml HNO₃, and 190ml water in plastic container.

Application Notes

Immerse 8–15 s at room temperature. Swab if needed. Rinse copiously with cold water; never alcohol-rinse aluminum.

Troubleshooting

HF burns may be delayed; keep calcium gluconate gel on hand. PE container only. Staining on 2024/2219/7075: switch to 0.5% HF.

Storage Notes

PE/PP bottle at room temperature, labeled with HF symbol. Stable many months.

Alternative Etchants

0.5% HF
Barker's Reagent (Electrolytic)
Al-NaOH Etchant

Similar Etchants

0.5% HF