If painted, use a solution of mild detergent and water, or a mild commercial cleaner whose label says it is safe for painted surfaces. Always rinse off solution. Wipe off excess water with a dry cloth. Do not use strong cleaners or scouring powder as these will damage the paint. If you plan to clean window frames, do it before cleaning window glass so solution does not spot glass panes.
Clear or colored anodized aluminum resists weathering, and can be washed with mild detergent and water like painted frames. Solvent cleaners can be used to remove grease spots from anodized frames. Never use abrasives on either anodized or painted surfaces as they will scratch it.
Bare, unfinished aluminum gradually weathers and turns gray. It forms its own oxide coating which protects it. (A coat of clear lacquer will prevent this.) In early stages of weathering, washing with soap and water will restore brightness. If you want to restore brightness when it has weathered more, stronger cleaners or mild abrasives will be needed. Test any new cleaner on a hidden spot to be sure it will work satisfactorily.
Do not clean aluminum if it is too hot to touch, or if temperature is below 50 F. Always remove all traces of cleaner thoroughly, with water-rinsing, or, if a solvent/wax type by wiping. Avoid excessive use of abrasives which leaves permanent scratches. Badly-weathered window frames may be washed with soap and water, rinsed thoroughly, and painted.
Anne Field, Extension Specialist, with credit to MSU Extension