What can be a metal cleanser for aluminum?
Really, ASTM procedures must be followed as written for certified testing. However, if this is for your edification or for a school project, you might use a commercial cleaner, such as those below, or just one ingredient such as phosphoric acid. 

There are a number of commercial aluminum corrosion cleaners, such as Loctite Duro Aluminum Jelly and CRC MaryKate Aluminex Clean and Shine. 

If you want to make your own:

Ingredients listed in the Aluminum Jelly Material Safety Data Sheet include phosphoric acid, diethyleneglycol monoethyl ether, nonionic surfactant, isopropyl alcohol , polysaccharide and sulfuric acid. [Similar formulaions may have contained hydrofluoric acid to break the highly-adherent $\ce{Al2O3}$ surface film and corrosion, but due to the hazards of $\ce{HF}$, I believe it is no longer sold in most places, for good reason.]

Aluminex Clean and Shine's MSDS includes ethoxylated tallow alkyl amines, sodium decylglucosides, hydroxypropyl phosphate and potassium iodide.