William R. Watt wrote:
I didn't know aluminum oxidized within minutes so I did a test.

Part of a piece of aluminum was scraped removing any oxidation and making
the scraped part bright and shiny. Two hours later the scraped part was
still just as bright and shiny. Eighteen hours later the scraped part was
not as bright and shiny. Part of the surface which had been scraped the
day before was rescraped and the difference was noticeable, the newly
scraped surface was brighter than the surface scraped the day before, but
both scraped surfaces were still a lot brighter than the part of the
surface which had not been scraped at all.

I would conclude that there is some oxidation in the first 24 hours.



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THe thin layer of oxide that forms in the first seconds is nearly
transparent. Try again, this time using a white piece of cloth. Polish
until the area seems as "bright and shiny" as you want. Notice the
black stuff on the cloth. That is aluminum oxide. Wait 30 seconds and
use a clean portion of the rag to polish the "bright and shiny" part you
just polished. Notice the black stuff? That is more aluminum oxide.

Aluminum is like silver. It oxidizes almost instantaneously.

It is this thin layer that fails when gluing parts. The adhesive bonds
to the oxide layer and the oxide fails, not the glue.



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