Here is what goes on.... I bend a thin wall brass tube to shape then I have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates the
pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is the
science behind this? Why does it plate?

LLB in Laredo

"LLBrown" wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then I
have to melt the bending medium out of the pipe with a torch. This
causes a black scaling to show up on the outside of the pipe. To remove
this I dip the pipe in a 50/50 mix of muratic acid and water. This in
turn plates the pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is the
science behind this? Why does it plate?

LLB in Laredo

It isn't plating. It's de-zincifying the brass. Muriatic eats zinc fast and
leaves a porous copper mess behind, which is very weak. When you buffed it,
you polished right through the porous copper again and got down to the
parent metal.

--
Ed Huntress

"Ed Huntress" wrote in message
...

"LLBrown" wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then I
have to melt the bending medium out of the pipe with a torch. This
causes a black scaling to show up on the outside of the pipe. To remove
this I dip the pipe in a 50/50 mix of muratic acid and water. This in
turn plates the pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is
the science behind this? Why does it plate?

LLB in Laredo

It isn't plating. It's de-zincifying the brass. Muriatic eats zinc fast
and leaves a porous copper mess behind, which is very weak. When you
buffed it, you polished right through the porous copper again and got down
to the parent metal.

--
Ed Huntress

Ed,
Thanks for your answer, I would be 100% convinced that your answer is
correct except this doesn't happen when the muratic acid is a new clean
batch. Why would that be?

LLB

"LLBrown" wrote in message
...

"Ed Huntress" wrote in message
...

"LLBrown" wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then I
have to melt the bending medium out of the pipe with a torch. This
causes a black scaling to show up on the outside of the pipe. To remove
this I dip the pipe in a 50/50 mix of muratic acid and water. This in
turn plates the pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is
the science behind this? Why does it plate?

LLB in Laredo

It isn't plating. It's de-zincifying the brass. Muriatic eats zinc fast
and leaves a porous copper mess behind, which is very weak. When you
buffed it, you polished right through the porous copper again and got
down to the parent metal.

--
Ed Huntress

Ed,
Thanks for your answer, I would be 100% convinced that your answer is
correct except this doesn't happen when the muratic acid is a new clean
batch. Why would that be?

LLB

Ah, well, now you've got me. It may be that there are copper ions in the
acid, if you've used it for that purpose before, and that they'll plate out
like electroless nickel. Now you'll need a chemist, which I definitely am
not. g

I have had a lot of experience with dezincified brass, however, and what
you're describing sounds like it to me.

--
Ed Huntress

LLBrown wrote:
"Ed Huntress" wrote in message
...
"LLBrown" wrote in message
...

...
I dip the pipe in a 50/50 mix of muratic acid and water. This in
turn plates the pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is
the science behind this? Why does it plate?


It isn't plating. It's de-zincifying the brass. ...


Thanks for your answer, I would be 100% convinced that your answer is
correct except this doesn't happen when the muratic acid is a new clean
batch. Why would that be?


My first guess would be a lack of observational rigor. Coupled with
slight differences in the situations, e.g., length of exposure.

The idea that "... acid is leaching copper and plating later pipes ..."
doesn't make sense. Why would it leach one, but not the other & why
would it plate one, but not the other?

"de-zincifying" is what I have always heard is happening. In support of
this is the fizzing that takes place. This is the hydrogen being
released from the muriatic acid (HCl) as zinc chloride is being formed.

Also not a chemist,
Bob

LLBrown wrote:
"Ed Huntress" wrote in message
...
"LLBrown" wrote in message
...

...
I dip the pipe in a 50/50 mix of muratic acid and water. This in
turn plates the pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is
the science behind this? Why does it plate?


It isn't plating. It's de-zincifying the brass. ...


Thanks for your answer, I would be 100% convinced that your answer is
correct except this doesn't happen when the muratic acid is a new clean
batch. Why would that be?


My first guess would be a lack of observational rigor. Coupled with
slight differences in the situations, e.g., length of exposure.

The idea that "... acid is leaching copper and plating later pipes ..."
doesn't make sense. Why would it leach one, but not the other & why
would it plate one, but not the other?

"de-zincifying" is what I have always heard is happening. In support of
this is the fizzing that takes place. This is the hydrogen being
released from the muriatic acid (HCl) as zinc chloride is being formed.

Also not a chemist,
Bob

In the music repair biz I have always hear it was plating and not dezinking.
Also, I have read many times that changing the bath will do away with the
problem. I am starting to think this is a folktale with no real science
behind it. Thanks for your answer.

LLB

"Bob Engelhardt" wrote in message
...
LLBrown wrote:
"Ed Huntress" wrote in message
...
"LLBrown" wrote in message
...

...
I dip the pipe in a 50/50 mix of muratic acid and water. This in turn
plates the pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is
the science behind this? Why does it plate?


It isn't plating. It's de-zincifying the brass. ...


Thanks for your answer, I would be 100% convinced that your answer is
correct except this doesn't happen when the muratic acid is a new clean
batch. Why would that be?


My first guess would be a lack of observational rigor. Coupled with
slight differences in the situations, e.g., length of exposure.

The idea that "... acid is leaching copper and plating later pipes ..."
doesn't make sense. Why would it leach one, but not the other & why
would it plate one, but not the other?

"de-zincifying" is what I have always heard is happening. In support of
this is the fizzing that takes place. This is the hydrogen being
released from the muriatic acid (HCl) as zinc chloride is being formed.

Also not a chemist,
Bob

In the music repair biz I have always heard it was plating and not
dezinking. Also, I have read many times that changing the bath will do away
with the problem. I am starting to think this is a folktale with no real
science behind it. Thanks for your answer.

LLB

"Ed Huntress" wrote:

Ed,
Thanks for your answer, I would be 100% convinced that your answer is
correct except this doesn't happen when the muratic acid is a new clean
batch. Why would that be?

LLB

Ah, well, now you've got me. It may be that there are copper ions in the
acid, if you've used it for that purpose before, and that they'll plate out
like electroless nickel. Now you'll need a chemist, which I definitely am
not. g

I have had a lot of experience with dezincified brass, however, and what
you're describing sounds like it to me.


Just to add a question to the question, what is the difference between inhibited muratic
and non-inhibited muratic?

I know we have some chemists on the list.

Wes

On Sat, 8 Nov 2008 14:58:28 -0600, "LLBrown"
wrote:

Here is what goes on.... I bend a thin wall brass tube to shape then I have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates the
pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is the
science behind this? Why does it plate?

LLB in Laredo

Its not plating.....hint..what is brass made of?

Which of the two metals is being removed by the acid?

Gunner

Political Correctness is a doctrine fostered by a delusional,
illogical liberal minority, and rabidly promoted by an
unscrupulous mainstream media, which holds forth the
proposition that it is entirely possible to pick up a turd by the clean end.

"LLBrown" wrote:

In the music repair biz I have always heard it was plating and not
dezinking. Also, I have read many times that changing the bath will do away
with the problem. I am starting to think this is a folktale with no real
science behind it. Thanks for your answer.

A few years ago uncle tried to fix a shallow well by pouring uninhibited muratic acid down
it. It didn't fix the well and I was surprised to see how the well pipe had rusted so
badly when he pulled it out of the ground. The muratic acid took the galvanized off near
the point.

There isn't plating going on, it is zinc being attacked.

Wes

I know we have some chemists on the list.

I guess I admit to being a chemist but I'm really rusty on this kind of
stuff. First, pure hydrochloric acid will not dissolve copper metal, but
hcl with oxygen dissolved in it will, so that is one difference between
fresh acid and "used" stuff. The used stuff most likely does have copper
ions dissolved in it. Then, since zinc is more electrochemically active
than copper, when you put the copper ions in contact with the zinc metal the
zinc is oxidized and the copper will plate out. Now, at the same time the
hcl is chewing up the zinc as fast as it can so it comes down to how "used
up" the acid is. If the hcl is mostly consumed so it doesn't react with the
zinc very fast, and if the solution has picked up lots of dissolved air
(oxygen) in use and then used that to dissolve lots of copper along the way,
that copper will have time to plate out on the zinc before the remaining hcl
eats away the zinc. If you took fresh hcl and just added pure zinc until
the acid was mostly used up, it should not plate copper out if you then put
it on brass. This is all my take on this without doing any research to back
it up, ymmv, it's worth what you paid for it, etc ;-).

-----
Regards,
Carl Ijames

"Wes" wrote in message
news
"Ed Huntress" wrote:

Ed,
Thanks for your answer, I would be 100% convinced that your answer is
correct except this doesn't happen when the muratic acid is a new clean
batch. Why would that be?

LLB

Ah, well, now you've got me. It may be that there are copper ions in the
acid, if you've used it for that purpose before, and that they'll plate
out
like electroless nickel. Now you'll need a chemist, which I definitely am
not. g

I have had a lot of experience with dezincified brass, however, and what
you're describing sounds like it to me.


Just to add a question to the question, what is the difference between
inhibited muratic
and non-inhibited muratic?

I know we have some chemists on the list.

Wes
I think inhibited muratic acid is saturated by dissolving all the zinc
possible in it. I think it is used to remove mineral deposits from
galvanized pipe and for soldering flux. I believe it is also called "killed"
acid.

Don Young

On Sat, 08 Nov 2008 16:21:49 -0500, Ed Huntress wrote:

"LLBrown" wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then I
have to melt the bending medium out of the pipe with a torch. This
causes a black scaling to show up on the outside of the pipe. To
remove this I dip the pipe in a 50/50 mix of muratic acid and water.
This in turn plates the pipe with very thin copper that I have to buff
off.

I know the acid is leaching copper and plating later pipes but what is
the science behind this? Why does it plate?

LLB in Laredo

It isn't plating. It's de-zincifying the brass. Muriatic eats zinc fast
and leaves a porous copper mess behind, which is very weak. When you
buffed it, you polished right through the porous copper again and got
down to the parent metal.

Apparently much of the "Aztec Gold" that the Spanish went chasing after
was naturally occurring copper-silver-gold alloy that they made their
objects out of, then soaked in a suitable solvent (one such "suitable
solvent" being, IIRC, **** that had been left in the bowl until it was
smelly -- I don't know if I'm _that_ dedicated of a metalworker).

The solvent would dissolve the copper and silver, leaving porous gold
behind. Then the craftsman would beat on the thing to crush the gold
into a nice solid-looking layer.

This is all recollection of an article read a looooong time ago, so if
someone has a more accurate reference share it, by all means.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Carl,
Thanks for this answer, I may not be nuts! : )

LLB

"Carl Ijames" wrote in message
...
I know we have some chemists on the list.

I guess I admit to being a chemist but I'm really rusty on this kind of
stuff. First, pure hydrochloric acid will not dissolve copper metal, but
hcl with oxygen dissolved in it will, so that is one difference between
fresh acid and "used" stuff. The used stuff most likely does have copper
ions dissolved in it. Then, since zinc is more electrochemically active
than copper, when you put the copper ions in contact with the zinc metal
the zinc is oxidized and the copper will plate out. Now, at the same time
the hcl is chewing up the zinc as fast as it can so it comes down to how
"used up" the acid is. If the hcl is mostly consumed so it doesn't react
with the zinc very fast, and if the solution has picked up lots of
dissolved air (oxygen) in use and then used that to dissolve lots of
copper along the way, that copper will have time to plate out on the zinc
before the remaining hcl eats away the zinc. If you took fresh hcl and
just added pure zinc until the acid was mostly used up, it should not
plate copper out if you then put it on brass. This is all my take on this
without doing any research to back it up, ymmv, it's worth what you paid
for it, etc ;-).

-----
Regards,
Carl Ijames

On Nov 8, 3:58 pm, "LLBrown" wrote:

Here is what goes on.... I bend a thin wall brass tube to shape then I have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates the
pipe with very thin copper that I have to buff off.

I'd be more concerned about annealing the tube during the melt-out,
countering
whatever work hardening happened during the bending. Unless an
annealed
condition of that particular part has been recommended by Sheldon the
Cat, its
dent susceptibility makes it somewhat less desirable.

But what about just buffing the scale off in the first place?

LLBrown wrote:

Here is what goes on.... I bend a thin wall brass tube to shape then I have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates the
pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is the
science behind this? Why does it plate?

LLB in Laredo


No it's leaching the zinc and leaving the copper.
...lew...

wrote in message
...
On Nov 8, 3:58 pm, "LLBrown" wrote:

Here is what goes on.... I bend a thin wall brass tube to shape then I
have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I
dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates
the
pipe with very thin copper that I have to buff off.

I'd be more concerned about annealing the tube during the melt-out,
countering
whatever work hardening happened during the bending. Unless an
annealed
condition of that particular part has been recommended by Sheldon the
Cat, its
dent susceptibility makes it somewhat less desirable.

But what about just buffing the scale off in the first place?

The annealed condition is ok. I tried buffing and it can be done, it is
just a question of time. 10 seconds in the bath takes the scale off and
then I just scrub it with a plastic scratch pad to take the worst of the
copper off, its very thin. The whole project is buffed when finished.
Using the acid really saves time and effort.

LLB

"Ed Huntress" wrote in message
...

"LLBrown" wrote in message
...
snip---

Ah, well, now you've got me. It may be that there are copper ions in the
acid, if you've used it for that purpose before, and that they'll plate
out like electroless nickel.

That's what is happening. Zinc on the surface is displacing the copper in
solution, so it is, indeed, plating the copper. This process is
commonly used in refining where recovery of values is accomplished with base
metals. Zinc is amongst the best possible choices.

Harold







Now you'll need a chemist, which I definitely am
not. g

I have had a lot of experience with dezincified brass, however, and what
you're describing sounds like it to me.

--
Ed Huntress

"Harold and Susan Vordos" wrote in message
. net...

"Ed Huntress" wrote in message
...

"LLBrown" wrote in message
...
snip---

Ah, well, now you've got me. It may be that there are copper ions in the
acid, if you've used it for that purpose before, and that they'll plate
out like electroless nickel.

That's what is happening. Zinc on the surface is displacing the copper in
solution, so it is, indeed, plating the copper. This process is
commonly used in refining where recovery of values is accomplished with
base metals. Zinc is amongst the best possible choices.

Harold

Thanks, Harold, and thanks to Carl (who owned up to being a chemist). I sort
of smelled like that to me, but doing chemistry by smell is not to be
advised. d8-)

So it sounds like there is some degree of dezincification and some degree of
copper plating going on, the relationship depending upon the state of the
hydrochloric acid solution. Interesting. It could almost get me interested
in chemistry.

--
Ed Huntress

"Ed Huntress" wrote in message
...

"Harold and Susan Vordos" wrote in message
. net...

"Ed Huntress" wrote in message
...

"LLBrown" wrote in message
...
snip---

Ah, well, now you've got me. It may be that there are copper ions in the
acid, if you've used it for that purpose before, and that they'll plate
out like electroless nickel.

That's what is happening. Zinc on the surface is displacing the copper
in solution, so it is, indeed, plating the copper. This process is
commonly used in refining where recovery of values is accomplished with
base metals. Zinc is amongst the best possible choices.

Harold

Thanks, Harold, and thanks to Carl (who owned up to being a chemist). I
sort of smelled like that to me, but doing chemistry by smell is not to be
advised. d8-)

So it sounds like there is some degree of dezincification and some degree
of copper plating going on, the relationship depending upon the state of
the hydrochloric acid solution. Interesting. It could almost get me
interested in chemistry.


Heh! Were it not for my years of refining experience, I wouldn't have had a
clue. I have never studied chemistry in my life, aside from taking one
quarter at the community college in Utah, just before I started using
cyanide for extracting values from gold ore. That was about 30 long years
ago, and I've forgotten everything I learned.

It's nothing short of amazing how one can learn processes without having a
fundamental understanding of why they happen.

Harold

Here is what goes on.... I bend a thin wall brass tube to shape then I have
to melt the bending medium out of the pipe with a torch. * This causes a
black scaling to show up on the outside of the pipe. *To remove this I dip
the pipe in a 50/50 mix of muratic acid and water. *This in turn plates the
pipe with very thin copper that I have to buff off.

Would a paint stripping gun get hot enough to remove your bending
medium without producing scale?
--Glenn Lyford

wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then I
have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates the
pipe with very thin copper that I have to buff off.

Would a paint stripping gun get hot enough to remove your bending
medium without producing scale?
--Glenn Lyford
I bet it would. My heat gun works great for mass de-soldering of old circuit
boards. I can just melt the solder, whack the board against something solid,
and all the components fall off.

Don Young

On 2008-11-11, Don Young wrote:

wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then I
have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates the
pipe with very thin copper that I have to buff off.

Would a paint stripping gun get hot enough to remove your bending
medium without producing scale?
--Glenn Lyford
I bet it would. My heat gun works great for mass de-soldering of old circuit
boards. I can just melt the solder, whack the board against something solid,
and all the components fall off.

I'm surprised that I haven't seen mention of Cerrobend here. It
is a low melting point alloy designed for the purpose. IIRC, it melts
below the boiling point of water, so you can extract it without getting
hot enough to generate scale. The one disadvantage to Cerrobend (and
several other Cerro alloys) is that they are quite expensive, so if you
need a large amount for your support, it will not be cheap. (However,
it is infinitely reusable -- just make sure that you melt it in a
non-metalic container -- porcelain, quartz, anything which will handle
boiling water and not be likely to form an alloy with your bending
support.

As for the solder melting -- that may be well below the melting
point of the alloy which you are using for bend support. *Good* solder
is (or was) something like 38/62 (I forget which side was tin) but that
was the percentage for the eutectic alloy -- the one with the lowest
melting point.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
"LLBrown" wrote:

Here is what goes on.... I bend a thin wall brass tube to shape then I have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates the
pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is the
science behind this? Why does it plate?

LLB in Laredo



Silly slightly off topic comment. I saw recently on "How It's Made," a
trombone factory where they used simple ol' ice to act as an
anti-collapse bending medium. Just fill the brass tubes with water,
freeze in liquid nitrogen, and then bend... let them melt and tada...
bent, non-collapsed tubes. Is this possibly something that could work in
your situation? LN is cheap and with a decent dewar, you could do a lot
of these in a short time, and no ugly chemistry needed to preserve the
chemistry/tone of your tubes.


-Dan

"Daniel Abranko" wrote in message
...
In article ,
"LLBrown" wrote:

Here is what goes on.... I bend a thin wall brass tube to shape then I
have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I
dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates
the
pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is
the
science behind this? Why does it plate?

LLB in Laredo
\
I suspect that it really doesn't plate. What I think happens is that the
acid dissolves the zinc out of the surface of the brass, and leaves the
copper behind. Buffing it up removes the zinc depleted layer so it gets back
to original brass colour.









Silly slightly off topic comment. I saw recently on "How It's Made," a
trombone factory where they used simple ol' ice to act as an
anti-collapse bending medium. Just fill the brass tubes with water,
freeze in liquid nitrogen, and then bend... let them melt and tada...
bent, non-collapsed tubes. Is this possibly something that could work in
your situation? LN is cheap and with a decent dewar, you could do a lot
of these in a short time, and no ugly chemistry needed to preserve the
chemistry/tone of your tubes.


-Dan

"Don Young" wrote in message
esprovideinc...

wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then I
have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates
the
pipe with very thin copper that I have to buff off.

Would a paint stripping gun get hot enough to remove your bending
medium without producing scale?
--Glenn Lyford
I bet it would. My heat gun works great for mass de-soldering of old
circuit boards. I can just melt the solder, whack the board against
something solid, and all the components fall off.

Don Young

Hi,
I can melt the pitch (tar) out ok with a heat gun but I have to get the
pipe red hot to turn residue into ash. This is for musical instruments so
the pipe has to be really consistant.
LLB

"DoN. Nichols" wrote in message
...
On 2008-11-11, Don Young wrote:

wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then I
have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I
dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates
the
pipe with very thin copper that I have to buff off.

Would a paint stripping gun get hot enough to remove your bending
medium without producing scale?
--Glenn Lyford
I bet it would. My heat gun works great for mass de-soldering of old
circuit
boards. I can just melt the solder, whack the board against something
solid,
and all the components fall off.

I'm surprised that I haven't seen mention of Cerrobend here. It
is a low melting point alloy designed for the purpose. IIRC, it melts
below the boiling point of water, so you can extract it without getting
hot enough to generate scale. The one disadvantage to Cerrobend (and
several other Cerro alloys) is that they are quite expensive, so if you
need a large amount for your support, it will not be cheap. (However,
it is infinitely reusable -- just make sure that you melt it in a
non-metalic container -- porcelain, quartz, anything which will handle
boiling water and not be likely to form an alloy with your bending
support.

As for the solder melting -- that may be well below the melting
point of the alloy which you are using for bend support. *Good* solder
is (or was) something like 38/62 (I forget which side was tin) but that
was the percentage for the eutectic alloy -- the one with the lowest
melting point.

Enjoy,
DoN.

I have never tried Cerrobend but other builders have warned me that getting
it out of the pipe is a pain sometimes because it almost acts as a solder
and binds to the brass. I am not sure what coating the pipe with oil would
do to the Cerro... if it would be good for more than one use.
LLB

"Daniel Abranko" wrote in message
...
In article ,
"LLBrown" wrote:

Here is what goes on.... I bend a thin wall brass tube to shape then I
have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I
dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates
the
pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is
the
science behind this? Why does it plate?

LLB in Laredo



Silly slightly off topic comment. I saw recently on "How It's Made," a
trombone factory where they used simple ol' ice to act as an
anti-collapse bending medium. Just fill the brass tubes with water,
freeze in liquid nitrogen, and then bend... let them melt and tada...
bent, non-collapsed tubes. Is this possibly something that could work in
your situation? LN is cheap and with a decent dewar, you could do a lot
of these in a short time, and no ugly chemistry needed to preserve the
chemistry/tone of your tubes.


-Dan

Dan,
On top end trumpets measurments have shown that ice bent parts have indeed
flattened out in the bent areas. There is even one company that offers to
round out these pipes... for a price. Ice is ok for student instruments
where a guy is just making one bend all day long over and over. I really
spend a lot of time adjusting fits and such and need a longer working time.

I do use ice if I need to adjust a pipe that has already had the tar melted
out. My problem with it is that my shop is about 110 degrees in the summer.
I am serious about that heat! Anyway, it is a big race to get the pipe out
of the house and into the shop before I have a pipe full of slush : )

LLB

"Grumpy" wrote in message
. au...

"Daniel Abranko" wrote in message
...
In article ,
"LLBrown" wrote:

Here is what goes on.... I bend a thin wall brass tube to shape then I
have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I
dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates
the
pipe with very thin copper that I have to buff off.

I know the acid is leaching copper and plating later pipes but what is
the
science behind this? Why does it plate?

LLB in Laredo
\
I suspect that it really doesn't plate. What I think happens is that the
acid dissolves the zinc out of the surface of the brass, and leaves the
copper behind. Buffing it up removes the zinc depleted layer so it gets
back to original brass colour.

Hi Grumpy,
Here is what one of the earlier letters said:


I guess I admit to being a chemist but I'm really rusty on this kind of
stuff. First, pure hydrochloric acid will not dissolve copper metal, but
hcl with oxygen dissolved in it will, so that is one difference between
fresh acid and "used" stuff. The used stuff most likely does have copper
ions dissolved in it. Then, since zinc is more electrochemically active
than copper, when you put the copper ions in contact with the zinc metal the
zinc is oxidized and the copper will plate out. Now, at the same time the
hcl is chewing up the zinc as fast as it can so it comes down to how "used
up" the acid is. If the hcl is mostly consumed so it doesn't react with the
zinc very fast, and if the solution has picked up lots of dissolved air
(oxygen) in use and then used that to dissolve lots of copper along the way,
that copper will have time to plate out on the zinc before the remaining hcl
eats away the zinc. If you took fresh hcl and just added pure zinc until
the acid was mostly used up, it should not plate copper out if you then put
it on brass. This is all my take on this without doing any research to back
it up, ymmv, it's worth what you paid for it, etc ;-).

-----
Regards,
Carl Ijames

"LLBrown" wrote in message
...

"DoN. Nichols" wrote in message
...
On 2008-11-11, Don Young wrote:

wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then I
have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I
dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates
the
pipe with very thin copper that I have to buff off.

Would a paint stripping gun get hot enough to remove your bending
medium without producing scale?
--Glenn Lyford
I bet it would. My heat gun works great for mass de-soldering of old
circuit
boards. I can just melt the solder, whack the board against something
solid,
and all the components fall off.

I'm surprised that I haven't seen mention of Cerrobend here. It
is a low melting point alloy designed for the purpose. IIRC, it melts
below the boiling point of water, so you can extract it without getting
hot enough to generate scale. The one disadvantage to Cerrobend (and
several other Cerro alloys) is that they are quite expensive, so if you
need a large amount for your support, it will not be cheap. (However,
it is infinitely reusable -- just make sure that you melt it in a
non-metalic container -- porcelain, quartz, anything which will handle
boiling water and not be likely to form an alloy with your bending
support.

As for the solder melting -- that may be well below the melting
point of the alloy which you are using for bend support. *Good* solder
is (or was) something like 38/62 (I forget which side was tin) but that
was the percentage for the eutectic alloy -- the one with the lowest
melting point.

Enjoy,
DoN.

I have never tried Cerrobend but other builders have warned me that
getting it out of the pipe is a pain sometimes because it almost acts as a
solder and binds to the brass. I am not sure what coating the pipe with
oil would do to the Cerro... if it would be good for more than one use.
LLB

Oil is the traditional barrier for bending tubing with Cerrobend, but NOT
detergent motor oil.

Here's an old technical report on bending tubing with Cerrobend:

http://www.canadametal.com/pdf/cerro_bending.pdf

It also mentions limitations with using pitch, lead, and sand as
alternatives.

I have a four-pound block of Cerrobend that I haven't used for years, but
one thing I remember from using it is that it is unusually liquid for a
metal when it's melted. Stainless steel containers are recommended for
melting it, although the low temperatures involved would allow the use of a
wide variety of materials. As you say, it will solder itself to some metals
unless you oil the surface first.

--
Ed Huntress

"Ed Huntress" wrote in message
...

"LLBrown" wrote in message
...

"DoN. Nichols" wrote in message
...
On 2008-11-11, Don Young wrote:

wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then I
have
to melt the bending medium out of the pipe with a torch. This causes a
black scaling to show up on the outside of the pipe. To remove this I
dip
the pipe in a 50/50 mix of muratic acid and water. This in turn plates
the
pipe with very thin copper that I have to buff off.

Would a paint stripping gun get hot enough to remove your bending
medium without producing scale?
--Glenn Lyford
I bet it would. My heat gun works great for mass de-soldering of old
circuit
boards. I can just melt the solder, whack the board against something
solid,
and all the components fall off.

I'm surprised that I haven't seen mention of Cerrobend here. It
is a low melting point alloy designed for the purpose. IIRC, it melts
below the boiling point of water, so you can extract it without getting
hot enough to generate scale. The one disadvantage to Cerrobend (and
several other Cerro alloys) is that they are quite expensive, so if you
need a large amount for your support, it will not be cheap. (However,
it is infinitely reusable -- just make sure that you melt it in a
non-metalic container -- porcelain, quartz, anything which will handle
boiling water and not be likely to form an alloy with your bending
support.

As for the solder melting -- that may be well below the melting
point of the alloy which you are using for bend support. *Good* solder
is (or was) something like 38/62 (I forget which side was tin) but that
was the percentage for the eutectic alloy -- the one with the lowest
melting point.

Enjoy,
DoN.

I have never tried Cerrobend but other builders have warned me that
getting it out of the pipe is a pain sometimes because it almost acts as
a solder and binds to the brass. I am not sure what coating the pipe
with oil would do to the Cerro... if it would be good for more than one
use.
LLB

Oil is the traditional barrier for bending tubing with Cerrobend, but NOT
detergent motor oil.

Here's an old technical report on bending tubing with Cerrobend:

http://www.canadametal.com/pdf/cerro_bending.pdf

It also mentions limitations with using pitch, lead, and sand as
alternatives.

I have a four-pound block of Cerrobend that I haven't used for years, but
one thing I remember from using it is that it is unusually liquid for a
metal when it's melted. Stainless steel containers are recommended for
melting it, although the low temperatures involved would allow the use of
a wide variety of materials. As you say, it will solder itself to some
metals unless you oil the surface first.

Anything bigger than about an inch and a half will split if you use
CerroBend Ed and oiling the part aids the bending process innumerous ways.
It isn't primarily to done to prevent adhesion but rather to promote
slippage. CerroBend won't stick well or "wet" much of anything.
The stuff expands .005 in/in at the eutectic point, which is 158 degrees F.
That's to much strain for larger cross sections.

CerroTru, OTOH, shrinks .0002 in/in in about six hours and the eutectic temp
is 136 degrees F.
The price of CerroTru is about five times the price of CerroBend because of
the indium and Bismuth content required to change the properties.

I paid 85.00 per pound in Feb. for 20 one pound bricks for a job.
Bolton Metals makes the stuff and their web site has a lot of information.

JC

"John R. Carroll" wrote in message
...

"Ed Huntress" wrote in message
...

"LLBrown" wrote in message
...

"DoN. Nichols" wrote in message
...
On 2008-11-11, Don Young wrote:

wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then
I
have
to melt the bending medium out of the pipe with a torch. This causes
a
black scaling to show up on the outside of the pipe. To remove this I
dip
the pipe in a 50/50 mix of muratic acid and water. This in turn
plates the
pipe with very thin copper that I have to buff off.


CerroTru, OTOH, shrinks .0002 in/in in about six hours and the eutectic
temp is 136 degrees F.
The price of CerroTru is about five times the price of CerroBend because
of the indium and Bismuth content required to change the properties.

I paid 85.00 per pound in Feb. for 20 one pound bricks for a job.
Bolton Metals makes the stuff and their web site has a lot of information.


Sorry Ed. I should have said CerroLow 136, not CerroTru.
Tru has a much higher eutectic temperature.

JC

"John R. Carroll" wrote in message
...

"Ed Huntress" wrote in message
...

"LLBrown" wrote in message
...

"DoN. Nichols" wrote in message
...
On 2008-11-11, Don Young wrote:

wrote in message
...
Here is what goes on.... I bend a thin wall brass tube to shape then
I
have
to melt the bending medium out of the pipe with a torch. This causes
a
black scaling to show up on the outside of the pipe. To remove this I
dip
the pipe in a 50/50 mix of muratic acid and water. This in turn
plates the
pipe with very thin copper that I have to buff off.

Would a paint stripping gun get hot enough to remove your bending
medium without producing scale?
--Glenn Lyford
I bet it would. My heat gun works great for mass de-soldering of old
circuit
boards. I can just melt the solder, whack the board against something
solid,
and all the components fall off.

I'm surprised that I haven't seen mention of Cerrobend here. It
is a low melting point alloy designed for the purpose. IIRC, it melts
below the boiling point of water, so you can extract it without getting
hot enough to generate scale. The one disadvantage to Cerrobend (and
several other Cerro alloys) is that they are quite expensive, so if you
need a large amount for your support, it will not be cheap. (However,
it is infinitely reusable -- just make sure that you melt it in a
non-metalic container -- porcelain, quartz, anything which will handle
boiling water and not be likely to form an alloy with your bending
support.

As for the solder melting -- that may be well below the melting
point of the alloy which you are using for bend support. *Good* solder
is (or was) something like 38/62 (I forget which side was tin) but that
was the percentage for the eutectic alloy -- the one with the lowest
melting point.

Enjoy,
DoN.

I have never tried Cerrobend but other builders have warned me that
getting it out of the pipe is a pain sometimes because it almost acts as
a solder and binds to the brass. I am not sure what coating the pipe
with oil would do to the Cerro... if it would be good for more than one
use.
LLB

Oil is the traditional barrier for bending tubing with Cerrobend, but NOT
detergent motor oil.

Here's an old technical report on bending tubing with Cerrobend:

http://www.canadametal.com/pdf/cerro_bending.pdf

It also mentions limitations with using pitch, lead, and sand as
alternatives.

I have a four-pound block of Cerrobend that I haven't used for years, but
one thing I remember from using it is that it is unusually liquid for a
metal when it's melted. Stainless steel containers are recommended for
melting it, although the low temperatures involved would allow the use of
a wide variety of materials. As you say, it will solder itself to some
metals unless you oil the surface first.

Anything bigger than about an inch and a half will split if you use
CerroBend Ed and oiling the part aids the bending process innumerous ways.
It isn't primarily to done to prevent adhesion but rather to promote
slippage. CerroBend won't stick well or "wet" much of anything.
The stuff expands .005 in/in at the eutectic point, which is 158 degrees
F. That's to much strain for larger cross sections.

CerroTru, OTOH, shrinks .0002 in/in in about six hours and the eutectic
temp is 136 degrees F.
The price of CerroTru is about five times the price of CerroBend because
of the indium and Bismuth content required to change the properties.

I paid 85.00 per pound in Feb. for 20 one pound bricks for a job.
Bolton Metals makes the stuff and their web site has a lot of information.

JC

I have a block of Cerrosafe, too, which first shrinks, then expands again to
zero net expansion, and then, after days, expands a bit. It's good for
casting impressions of rifle chambers if you get the timing right.

They're all interesting materials but they're not for the uninitiated. As
for the sticking, I haven't had the problem because I've only cast it in
plaster, for making jigs for some handiwork projects for my wife and her
friend. I lacquered and waxed the plaster and that kept it from sticking.

I inherited both of those blocks, BTW. Cheap as I am, I don't think I would
have bought the stuff.

--
Ed Huntress

"Glyford" fired this volley in news:JNgSk.5058$W06.1154
@flpi148.ffdc.sbc.com:

This in turn plates
the
pipe with very thin copper that I have to buff off.


Not exactly. It dissolves the zinc, leaving copper behind. There's no
copper in muratic acid with which to plate the tubing.

LLoyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"Glyford" fired this volley in news:JNgSk.5058$W06.1154
@flpi148.ffdc.sbc.com:

This in turn plates
the
pipe with very thin copper that I have to buff off.


Not exactly. It dissolves the zinc, leaving copper behind. There's no
copper in muratic acid with which to plate the tubing.

LLoyd

LLoyd, thanks for your letter. I think the acid picks up copper during the
process of cleaning 30 or 40 pipes. New acid doesn't cause this problem,
just older "spent" muratic. I will change acid after this horn and give
everyone a report on using fresh stuff.

Regards,
LLB

On Nov 11, 10:12 am, "John R. Carroll"
wrote:

Anything bigger than about an inch and a half will split if you use
CerroBend Ed

Have to disagree, as my french horn bell section did not, despite
having a longitudinal brazed seam. Of course the bend radius was
rather large and it only got that big in diameter towards the end.

Took all my weight on the steel bar I cast sticking out the open end
to finish the bend though.

On Nov 11, 9:38 am, "LLBrown" wrote:

I can melt the pitch (tar) out ok with a heat gun but I have to get the
pipe red hot to turn residue into ash. This is for musical instruments so
the pipe has to be really consistant.

I always wondered about getting it a bit less hot and blowing oxygen
through it...

....carefully of course, as I can imagine a number of ways it could get
real exciting real quickly.

wrote:
On Nov 11, 10:12 am, "John R. Carroll"
wrote:

Anything bigger than about an inch and a half will split if you use
CerroBend Ed

Have to disagree, as my french horn bell section did not, despite
having a longitudinal brazed seam. Of course the bend radius was
rather large and it only got that big in diameter towards the end.

Took all my weight on the steel bar I cast sticking out the open end
to finish the bend though.

Musical instruments are generally conical in cross section so the alloy has
the opportunity to displace and avoid damagind the part.
I sent Ed three pics of a part I finished recently that was filled with
Cerrelow 136. Test parts filled with CerraBend just ruptured. The volume,
however, was nearly closed and it was also fairly large.
Hey, if you want to have some fun sometime, take a Cerrabend filled part and
quench it in ice water!
The result looks like something that's been through a hail storm.
LOL

--

Dick

"Dick 'Tater" wrote in message
...
wrote:
On Nov 11, 10:12 am, "John R. Carroll"
wrote:

Anything bigger than about an inch and a half will split if you use
CerroBend Ed

Have to disagree, as my french horn bell section did not, despite
having a longitudinal brazed seam. Of course the bend radius was
rather large and it only got that big in diameter towards the end.

Took all my weight on the steel bar I cast sticking out the open end
to finish the bend though.

Musical instruments are generally conical in cross section so the alloy
has
the opportunity to displace and avoid damagind the part.
I sent Ed three pics of a part I finished recently that was filled with
Cerrelow 136. Test parts filled with CerraBend just ruptured. The volume,
however, was nearly closed and it was also fairly large.
Hey, if you want to have some fun sometime, take a Cerrabend filled part
and
quench it in ice water!
The result looks like something that's been through a hail storm.
LOL

And that's one heck of an impressive part, too. It looks like something that
would be sitting under you if you rode a rocket into orbit.

--
Ed Huntress

On Nov 12, 2:32 am, "Dick 'Tater" wrote:
wrote:
On Nov 11, 10:12 am, "John R. Carroll"
wrote:

Anything bigger than about an inch and a half will split if you use
CerroBend Ed

Have to disagree, as my french horn bell section did not, despite
having a longitudinal brazed seam. Of course the bend radius was
rather large and it only got that big in diameter towards the end.

Took all my weight on the steel bar I cast sticking out the open end
to finish the bend though.

Musical instruments are generally conical in cross section so the alloy has
the opportunity to displace and avoid damagind the part.
I sent Ed three pics of a part I finished recently that was filled with
Cerrelow 136. Test parts filled with CerraBend just ruptured. The volume,
however, was nearly closed and it was also fairly large.
Hey, if you want to have some fun sometime, take a Cerrabend filled part and
quench it in ice water!
The result looks like something that's been through a hail storm.
LOL

--

Dick