Been taking out the windows and cleaning the Al.window frames with steel wool and polish. but the pitting and oxidation was tough to remove. Tried scraping it but left marks, soooo .I tried a bathroom tub and tile cleaner. The one I used was called eliminator from our good friends at HD. Applied it with the steel wool and it worked great --took the oxidation off!!! Just a teaspoon did it. Then polished with what ever!!!