BoatBanter.com - View Single Post - Anybody tried glueing cast aluminum parts together with epoxy?

On 15 Oct 2005 14:53:26 GMT, (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.

If you can't see the film, doesn't mean it's not there.
Astro mirrors are aluminized, these days.
In a vacuum chamber, a small aluminum sample is vaporized off a
filament onto the glass.
Then they let the air back in. That mirror surface looks good for
years. And if they hard coat it, it lasts even longer.

Brian W