2% HF (Alpha Case)

• ASTM formula 11, attacks FeAl₃, other constituents outlined. It contains hydrofluoric acid as the name implies.

AWS D1.2 Basic Etchant

• A macro etchant for visual inspection of aluminum, listed in AWS welding code D1.2. It does NOT contain hydrofluoric acid.

Barker’s Reagent

• ASTM formula 5, an electrolyte for electrolytic etching pure aluminum, 1000, 3000, 5000, 6000 and 7000 series. Need a polarized light microscope to see the result.

Keller’s Reagent

• ASTM formula 3, the most popular general-purpose micro etchant for aluminum alloys, shows microstructure and grains. It contains hydrofluoric acid.