A Method for the Isolation of Surface Films from Aluminum Alloys and the Mechanism of the Reactions Involved

Abstract

Warm solutions of iodine in methanol were found satisfactory for isolating surface films from aluminum alloys not containing copper. Addition of sulfosalicylic acid to these solutions renders them satisfactory for isolation of films from aluminum‐copper alloys. Attack is not selective at the film‐metal interface, so all aluminum must be dissolved before uncontaminated films can be obtained. Hydrogen evolved during dissolution of the aluminum is believed due to the formation of aluminum methoxide. Iodide ions are also formed in these solutions. Aluminum methoxide is insoluble in dehydrated solutions but is decomposed by traces of water to soluble reaction products. A mechanism for the dissolution of aluminum in iodine‐methanol solutions is suggested.