How fast does a fresh extrusion of 6063 oxidize, and how thick will that oxide coating get?

摘要

The natural oxide forms readily since the reaction of elemental aluminum with oxygen is highly exothermic. According to Karl Wefers, in "Oxides and Hydroxides of Aluminum", Alcoa Laboratories, 1987: "Oxide layers developing near room temperature in oxygen or dry air reach a limiting thickness of 2 to 4 nm after several hours." If the oxide is formed at higher temperatures, it will be thicker. According to Surface Treatment and Finishing of Aluminum and Its Alloys, by S. Wernick, R. Pinner, and P. G. Sheasby, 5th edition, ASM International and Finishing Publications, 1987, the natural oxide formed at temperatures above 300 deg C can be up to 30 nm thick.