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Anodizing small niobium tube in silver brooch


#1

Hi,

I need help to anodize a 4mm piece of niobium tube, which circles a
stg silver rod, in a stg silver brooch. I have tried following Bill
Seeley’s instructions but had no luck so far. I have cleaned/filed
back the niobium tube after all the soldering, and then tried to
anodize it by pinching the ferrule of a painting brush with the
cathode. Dipped the brush into the mixture, but nothing happens.
Have also tried wrapping a piece of titanium around a wet cotton bud,
then clamping the cathode onto the titanium, but still no joy. If I
put the object in the bath and anodize it the conventual way with the
anode, then the object will be a huge job to clean back to stg
silver. The niobium tube is loose around the silver rod. Is what I
want to do feasible?. All help appreciated.

Felicity in autumnal Perth West Australia


#2
I need help to anodize a 4mm piece of niobium tube, which circles
a stg silver rod, in a stg silver brooch. 

In my experience, the only way you will be able to do this is if you
can isolate the niobium electrically from the silver. If you can
coat the silver with tape, rubber cement, wax, or some other
non-conducting material, or insert electric tape between the two
metals so that they do not touch at all, you should be able to
anodize normally. Otherwise, it seems as though the current just
goes through the silver, turning it black, and not affecting the
reactive metal at all.

Good luck!
Noel


#3

Felicity, I just have 4 quick comments.

1). If Bill S gives you advice, if you follow it faithfully it’s
going to work - he has “been there and done that”.

2). If the niobium tube was heated during fabrication, it can take on
an oxide that will prevent anodizing to color.

3). When you “painted” with a wet paintbrush connected to the
cathode, did the piece have a good electrical path to the anode? Did
you see bubbles forming at the higher voltages?

  1. I am not convinced that you could not immerse the entire piece and
    not damage the sterling finish, if there is any change you might be
    able to reverse the polarity and ionic clean or electrostrip any
    tarnish.

Let us know how you solve this problem.

Marlin, back from the Bench Conference Expo here in Denver and
dreaming of too many new tools!


#4

Hi Martin,

Thanks for the response… Think my “falling down” might be your No
3. question.

When you "painted" with a wet paintbrush connected to the cathode,
did the piece have a good electrical path to the anode? Did you
see bubbles forming at the higher voltages? 

Bill’s book says use the paint brush method with the brush connected
to the cathode… However does that mean that I should connect the
anode to the titanium strip which is in the bath. Usually it is the
other way round… I.e. cathode to bath and anode touches the object
in the bath to cause the colouring. I couldn’t see any bubbles
forming around the brush or in the bath…Your help is much
appreciated.

Felicity in Sunny Perth West Australia


#5
I couldn't see any bubbles forming around the brush or in the
bath.. 

When you use a brush, you don’t use a bath. Maybe you didn’t read the
instructions quite carefully enough. With a brush, you attach the
anode to the piece, and the cathode to the brush. You wet the brush
with the conductive material that you normally use in the bath. When
you touch the brush to the niobium, that completes the circuit.

Noel


#6

Ahhh, the most common mistake rears its lovely head! The process is
called anodizing and the work/color always appears at the Anode(+).
When you are working with a brush(Cathode[-]) the object being
colored (Anode[+]) is outside the bath. The electrolyte is on the
brush in contact with the metal ferrule(Cathode[-]). The object is
connected to the Anode(+). Look at the brush is a miniature portable
bath. Instead of the container and metal strip the hairs of the
brush hold the electrolyte and they are in contact with the
Cathode(-)/metal ferrule. Don’t worry, I hook them up backwards at
some point in every workshop and I have been doing that for 26 years!

Bill

Thank you, Bill, Deborah, Michele & Sarah
Reactive Metals Studio, Inc.


800/876-3434 - 928/634-3434 - F928/634-6734


#7

Felicity,

After I sent the reply email about anodizing, I thought I would give
it a go to see what happens. After a frustrating 30 minutes, I came
to the same conclusion as your last post. Attach the brush to the
cathode (is it now cothodizing? :slight_smile: and it works great. I had a heck
of a time coming to this conclusion. I thought my power supplies or
my brushes were bad, but I could bath anodize Tantalum, Titanium and
Niobium - but no luck with the brush, something I have done many
times - until I reversed the polarity. Anode to piece, cathode to
brush. It worked fine.

A couple of possible trouble spots would be if the electricity
"shorts" through the silver. The colors on the reactive metals
develop because as the oxide layer forms, it provides an increasingly
resistive layer. silver will not do that, so if too much silver is in
contact with the solution, it just shunts through the solution to the
silver.

I also tried the bath method (which I suggested might not harm the
silver). DON’T DO IT. The result is some strong discoloration which
does not go away with reverse polarity. There may be solutions out
there that would work (Speed Brite?), but neither TSP nor NaHCO3
(baking soda) are friendly to the silver. They may well lead to a
useful patina however.

At least I was able to do the anodizing with a brush on the Ag/Ti
piece.

Marlin, in a cool rainy Denver
I


#8
I also tried the bath method (which I suggested might not harm the
silver). DON'T DO IT. The result is some strong discoloration
which does not go away with reverse polarity. 

I guess this is my opportunity to say “I told you so!” (Hard to
resist.)

Attach the brush to the cathode (is it now cothodizing? :-) 

If you remember that it is anodizing, you won’t get mixed up-- the
reactive metal piece is still (always) the anode. The cathode is the
"wet" part, be it bath or brush.

Glad it worked.

–Noel


#9

To Noel, Marlin and dear Bill!

Many thanks, The anodising worked a treat. Very happy with the
result…

Thanks everyone
Felicity in sunny Perth Western Australia