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From: henry@zoo.toronto.edu (Henry Spencer)
Newsgroups: sci.military
Subject: Re: Aluminum Ships
Message-ID: <1990Jun30.053937.4645@cbnews.att.com>
Date: 30 Jun 90 05:39:37 GMT
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From: henry@zoo.toronto.edu (Henry Spencer)
>From: raymond%carme@uunet.UU.NET (Raymond Man)
>We need to talk to chemists here. I believe (from what remain of my
>high school chemistry) that Al reaction with O is exothemric...
>... For steel, I believe it is endothermic...

Not so.  Any metal reacting with oxygen is exothermic, often highly so.
Steel wool can burn quite impressively.  Differences lie in how easy the
metals are to ignite.  Steel wool is an extremely favorable case because
it's finely-divided steel with lots of oxygen around it.  It is *very*
difficult to ignite bulk steel, to the point where it essentially never
happens.  And it is actually very difficult to ignite bulk aluminum,
for that matter -- last I heard, there are *no* known confirmed cases
of aluminum fires in warship accidents.

As our moderator mentions, one important factor in the case of aluminum
is its very tough oxide film.  You've never touched aluminum.  For that
matter, you have probably never touched steel or magnesium.  What you
touch is the oxide film on the surface.  But the physical properties
of that oxide film vary a lot depending on the metal (which is why, for 
example, steel rusts -- spontaneously "burning" at an infinitesimal
rate -- and aluminum doesn't).

                                         Henry Spencer at U of Toronto Zoology
                                          henry@zoo.toronto.edu   utzoo!henry