1) Keller's reagent

2) 0,5 ml HF + 99,5 ml H2O

Dear Krzysztof,

Thank you for your answer.

Keller's etching reagent is best suitable for most of the aluminum alloys. Distilled water (95%) + Nitric acid (2.5%)+ Hydrochloric acid (1.5%)+ Hydrofluoric acid (1%).

You can try the following solution also,

Methanol (25 ml)+ Hydrochloric acid(25ml) + Nitric acid(25ml)+ Hydrofluoric acid (2-3 drops)