the accidental plater

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.

Reply to
DoN. Nichols
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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

Reply to
Daniel Abranko

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.

Reply to
Grumpy

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

Reply to
LLBrown

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

Reply to
LLBrown

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

Reply to
LLBrown

Hi Grumpy, Here is what 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

Reply to
LLBrown

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:

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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

Reply to
Ed Huntress

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

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

LLoyd

Reply to
Lloyd E. Sponenburgh

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

Reply to
LLBrown

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.

Reply to
cs_posting

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.

Reply to
cs_posting

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

Reply to
Dick 'Tater

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

Reply to
Ed Huntress

Reply to
cs_posting

I always quenched the parts - think I waited a few seconds after filling, then dropped them into a much larger pipe full of cold tap water. For the bell section I think I had the garden hose running to refill the pipe. Not as fast as ice water I suppose, but then it's not all that hot to begin with.

But the tubing was annealed first. The amount of growth on cooling really isn't that significant - however, the behavior of the filler as it is bent is, and that can depend on how it cools.

Reply to
cs_posting

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