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Metals-Aluminum and?

Hi R.R., You’ve asked a good question here and I don’t know if I
have all the answers you need, but here goes.

To start off, I have done a bit of work in both copper and brass and
have found that, while some people hate these matals turning them
green, other folks say they don’t mind a bit. I’m serious, the
groups seem to be split about 50%-50%. Both metals age very nicely
if properly taken care of. That’ll be the domain of care that sits
in the customer’s realm. There are no guarantees there. Both metals
can be colored or treated in a variety of ways that produce
beautiful results. On the downside, I’ve run into a snobbish
attitude in some folks that consider them to be base metals not
worthy of being called jewelry. Go figure… Anyway, about aluminum-
This metal also produces an oxide. It is white and I have no idea
what kind of allergic reactions someone may have with it. It may be
able to be sealed in some fashion but, depending on the design and
how much abuse/wear it will take, sealants have a way of wearing off
eventually. Check the Orchid archives because there has been a great
deal of conversation on differing metals. Jim Binnion and John
Burgess have offered a great many good insights on the topic. I’ve
learned a great deal from their posts. Interestingly, on a side
note, I had a machinist friend once that said that aluminum has an
interesting talent. It will grow an oxide layer that will eventually
get thick enough to stop contact between oxygen and the metal and
stop growing. He said he’s used it in a number of applications
because of that very trait. It oxidizes till it can’t oxidize any
more and then it stops. One thing to think about with aluminum is
that, when brought into contact with a different metal and exposed
to good ol’ human sweat, a galvanic reation takes place that can
cause serious corrosion. It can be mixed with stainless steel
without much problem though. They use it in this combination on
sailboats quite a bit for this reason.

As far as gunmetal goes, I think it is a type of bronze and it too
will oxidize. If I’m not mistaken it too goes green on the skin. I
could be wrong on this one.

I’ve never worked with titanium. It might be the cat’s meow. I just
don’t know You might entertain the idea of stainless steel as a
medium though. It’s tough stuff and, to my knowledge, fairly inert
in contact with other metals.

Along the lines of allergic reactions, my wife can’t wear nickle or
anything Rhodium plated. Both cause big problems for her. Good luck
in your search for answers. Try a search of the archives for the
metals you have questions about. Lot’s of good lives in
the archives.

Mike

G’day;

Michael Honeycut is quite correct in his comments about aluminium
oxide forming a protective layer on freshly exposed aluminum metal.
In fact, one Stage 2 chemistry question set in an exam asked, “Would
a roof made of aluminium dissolve in a heavy downpour of rain?
Explain your findings in complete detail with formulae and
mathematical reasoning.”

The answer is that according to it’s theoretical chemical reactions
with water it should dissolve but does not because a thick layer of
aluminium oxide is formed on immediate exposure to moist air which
completely protects the metal from further reaction. Which is one
reason why ordinary lead-tin solder won’t join the metal or even
adhere to it. It is possible to get lead-tin to solder it, if it can
only contact the bare metal. A strongly vibrating soldering iron can
manage that, but it isn’t satisfactory. Welding supply companies will
supply a special alloy rod together with a special flux which can
produce a very good join, in aluminium, much like a brazed joint in
copper. brass or steel. I have done this many times, but a very small
hot flame is necessary. Propane/oxygen is excellent.

Cheers for now,
JohnB of Mapua, Nelson NZ

One very small contribution to this discussion of different metals–
aluminum can be enamelled. I attended a brief workshop with it years
ago. I don’t remember details-- I know you need to be careful not to
overheat the aluminum because it melts and, I think, gives off toxic
fumes, but we used the same enamels as for copper and torch fired
them. It was funky-looking, and I didn’t pursue it. For what it’s
worth!

–Noel