On Tue, 21 Dec 2010 13:17:11 -0500, "Phil Kangas"
wrote:


"Pete Keillor" wrote
in message
.. .
On Tue, 21 Dec 2010 06:00:10 -0500,
lid wrote:

On Mon, 20 Dec 2010 21:12:54 -0500, "Phil
Kangas"
wrote:

I'm going to try this url to see if it works.
This video is of mercury attacking aluminum.
Can you explain the reaction?
phil k.



http://tinyurl.com/286pl63




And now you know why it is illegal to bring
mercury filled
thermometers onto commercial aircraft flights.
Dave

Just a guess. If mercury alloys with or
dissolves aluminum, then the
dissolved aluminum would react rapidly with
oxygen to aluminum oxide,
and being dissolved be unable to form the tough
aluminum oxide coating
that normally stops this reaction. So the
aluminum is depleted in
solution, more dissoves, and so on.

Pete Keillor

So the mercury has a greater affinity for oxygen
than the
aluminum? What is the grey matter produced from
the
reaction? Is it a hazardous substance?
phil k.


No, I don't think the mercury is oxidizing. It's just providing a
source of aluminum to oxidize, and the aluminum can't form a stable
oxide coating, which on bare aluminum happens in seconds. The only
role of the mercury is to form a semiliquid alloy with the aluminum,
and keep doing that as aluminum in the alloy reacts with oxygen.

If I'm correct, the grey stuff would just be aluminum oxide, probably
contaminated with mercury. The mercury would make it hazardous.
Aluminum oxide by itself is a very good insulator to very high
temperatures, also very good against corrosion. Which is why when it
forms directly on aluminum metal it protects the metal quite well. It
just can't form a tightly bonded layer to aluminum when forming on the
mercury alloy.

In 1980 I worked on an experimental cell to electolytically produce
magnesium and chlorine gas from a molten salt bath at 700 C. Steel
lasted days at best in there. The 99.5% alumina (aluminum oxide)
brick the cell was constructed from was as good at shutdown as when
the thing was constructed. There were about 200,000 bricks in that
cell. It wasn't cheap.

Pete Keillor