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Aluminum - safety, annealing, pickling, coating


#1

Hello Everyone,

I’m a very amateur metalsmith, so I apologize if this has been
covered already. I’m just learning how to navigate the archives and
forum.

I learned how to forge and anneal silver, copper, and brass recently,
and while I was perusing the hardware store racks for practice
material, I spied some aluminum and the wheels started turning. I do
all my work outside, sheltered from the elements and fur-children,
but well ventilated. My usual setup is to mark the item I’m annealing
with a sharpie, torch it till the sharpie mark goes away, dunk it in
a water bath immediately, then into a Sparex No 2 pickle bath it
goes. I keep two crockpots with pickle going–one with hydrogen
peroxide added in for my brass and copper, one without for Silver
only.

  1. Are there any safety considerations I need to consider for
    working with aluminum, whether I’m cutting, torch annealing, or
    pickling?

  2. Will the same Sharpie trick work?

  3. Do I still dunk it in the water bath, or do I let it air cool?

  4. Can I use Sparex, or do I need to use a different pickle, and if
    so, what (or what recipe)?

  5. When I’m done with a piece of wearable art, do I need to coat the
    aluminum with anything?

Thanks in Advance,
Kristen


#2

Aluminium is annealed at much lower temperatures than copper or
brass, and the Sharpie trick won’t work. A good method is to leave a
streak of soap on the ally and heat it until the soap turns black,
then dunk it in water. Aluminium oxide forms almost immediately at
room temperature and cannot be removed by normal pickle.

The normal way to treat aluminium is by anodising it. It can then be
dyed or left natural

Regards, Gary Wooding


#3

To get the correct annealing tempeasture for aluminium mark the metal
with a bar of soap and hea from the opposite side. When the soap mark
turns black you have reached the correct temperature. Plunge into
cold water. DO NOT use ny pickling baths used for other metals, you
will dissolve the aluminium and ruin the pickle as well. Removing the
oxide from Al is best done mechanically with abrasive paper. It is
impossible to stop aluminium from oxidising so choose your alloy to
avoid those containing magnesium or lithium as these will corrode in
no time at all. I cannot think of anything that would make a good
coating for your finished work but suggest that you do a final polish
with colloidal silica. This is available from Buehler or similar
metallurgical polishing suppliers.

Nick Royall


#4

Avoid using caustic soda (lye) products to clean aluminium - it
reacts with the metal and releases hydrogen. On the plus side, in a
very well vented area, you could probably use that chemical
reaction to texture the surface.

Jamie
http://primitive.ganoksin.com


#5
Avoid using caustic soda (lye) products to clean aluminium - it
reacts with the metal and releases hydrogen. On the plus side, in
a *very* well vented area, you could probably use that chemical
reaction to texture the surface. 

When you etch silver with nitric acid you release hydrogen.