Can you remove solder chemically?

[Steve Broady]

Right off the bat, let’s not start an argument about safety here. I am trying to REMOVE unsafe materials, and potentially teach others here how to do the same. I know there are some cheap copper alembic stills out there that might have an issue similar to mine, so I may not be alone here.

I have an 8” copper float ball that I would like to turn into an onion/expansion chamber/still bling, if it is practical to do so. Testing revealed the presence of lead in the solder. No reaction to the copper itself. I checked, just in case it was a terrible alloy. I’ve taken it apart into two hemispheres with the intention of just mechanically abrading away the solder to leave bare copper. That may still be the plan, but I’m considering less destructive avenues if possible. The copper is very thin, and very soft. It was strong enough as a ball, but I can see the potential for mangling this thing while it’s separated.

Unfortunately, web searches for removing solder yield a lot of nonsense that seems to have been written by AI, or by a moron without any solid knowledge of plumbing, chemistry, or English. I found some tantalizing references to “desoldering paste” or “solder stripper,” but I can’t find any actual product by that name. I did find some folks using either mystery solution or diluted muriatic acid to dissolve tin solder from circuit boards.

Does anyone here have any experience trying to dissolve solder off of copper, without damaging the copper? I am tempted to try dropping a scrap of copper pipe with solder in some HCL to see what happens.

[MooseMan]

As you mentioned, HCL will dissolve solder, the precious metal recovery hobbyists use it specifically for that purpose.

But my now almost forgotten metallurgy knowledge is telling me that it will also eat your thin copper. I may be wrong here though, so your test would be a good idea.
Maybe file some thin areas on the pipe to see if it eats through.

Caveat here with HCL, don't do it anywhere near anything made of metal, that you care about.
If it were me, it would be in a triple bucket, as far away from everything as I could get.

[Salt Must Flow]

I would do that test Steve Broady.

I've done a lot of solder removal and if I'm being real careful, I use a Die Grinder and pads which are mildly mildly abrasive. They're not like sand paper, they're similar to Scotch-Brite scouring pads if that makes sense. I've even used a small wire wheel (I think stainless) on a Dremel tool at high speed.

If I'm being ultra careful, I'll heat the copper up and shake off any excess solder. I'll heat it again and wipe the area using a dry scrap towel. That wipes the copper as thin as I can make it. That makes gentle removal methods even easier.

Even if you will be using a chemical method of removal, the thinner the solder the better I imagine.

[Tammuz]

Braided copper wire will soak up solder, as will stranded copper wire. A shop vac with small tubing taped to the hose will also suck up liquid solder.

[Steve Broady]

If I'm being ultra careful, I'll heat the copper up and shake off any excess solder. I'll heat it again and wipe the area using a dry scrap towel. That wipes the copper as thin as I can make it. That makes gentle removal methods even easier.

Even if you will be using a chemical method of removal, the thinner the solder the better I imagine.

Yeah, no matter what I do I’ll be removing just as much as possible simply by melting and moving it. And the abrasive pads are pretty much exactly what I was going to use.

MooseMan, removing the copper is my concern as well. If we’re talking about a few microns, no biggie. But a significant portion of the material? That gets to be an issue. I suspect that no matter what I do, there will be some degree of damage to the copper. Whether it’s significant or not is the question.

[Dancing4dan]

I have done some solder / tin removal from copper using reversed polarity brush electroplating. Not difficult but it is slow. Clean off as much as you can with heat first. This is a picture of a copper vessel that was tinned and I removed the tin from the lid so far.

There is a solution that can be made from Oxalic acid, trisodium phosphate and ammonium sulfate. All available on Amazon. This expired patent application contains the solution formula I used.

Ventilation and PPE is required. Gloves and eye protection.

https://patents.google.com/patent/US723 ... 35%2c165B2

You need a small power source. I use a 30V 5amp power supply available from Amazon.

[MooseMan]

Dan that's cool AF!

[Reefer1]

There is a product called solder wick as Tummaz says when i was working on circuit boards i used to use, occasionally just heat up and put the wick on it not perfect but it may take enough out for you to resolder with lead free, dont know how effective it would be.

Not really heard of any chemical that you could used realistically without damaging the copper.

[The Maple Curtain]

There is a product called solder wick as Tummaz says when i was working on circuit boards i used to use, occasionally just heat up and put the wick on it not perfect but it may take enough out for you to resolder with lead free, dont know how effective it would be.

Not really heard of any chemical that you could used realistically without damaging the copper.

Solder wick will work to remove the bulk of material. Search for local electronic shops or online.

However there will be a thin coat of solder or tinning that will remain. Most likely this will need to be removed mechanically.

I used to work making prototype circuit boards in the 90's. It's amazing how much solder wick will clean up your contacts.

This is where I would buy it back in the day.

https://shop.sayal.com/search?q=solder+wick

[Demy]

Not chemical but practical. Heats the part, with a large cotton cloth passes on the semi liquid welding, careful not to burn you, use thick gloves. This will remove a large part of the thickness of the welding, you will only remain a thin veil that you can remove with sandpaper

[Reefer1]

+1 on that method Demi i use that same method for cleaning copper pipes that have been desoldered.
It do's still leave a tinning behind but it's minute.

[BritishChemist]

Archaeologists sometimes need to remove lead from artefacts without damaging the other metals it is in contact with. Here's a paper on some chemical removal options:
https://pmc.ncbi.nlm.nih.gov/articles/PMC7764096/

[jonnys_spirit]

Even if you remove some of the excess solder, you’ll want to remove a layer of copper where the bond occurred in order to clean up the lead contamination. Re-testing for lead recommended >

—— snip ——
Yes, when soldering, the molten solder creates a molecular bond with the metals it is joining, essentially forming a metallic bond at the atomic level by wetting the surfaces and filling the gaps between the metal pieces as it solidifies; this is why soldering creates a strong connection between different metals.
Key points about soldering and molecular bonds:
Metal-to-metal interaction:
When solder melts and flows into the joint, its atoms interact with the atoms of the base metals, forming a bond at the interface.
Capillary action:
The molten solder is able to penetrate tiny gaps between the metals due to capillary action, further enhancing the bond.
Flux role:
Flux is used to clean the surfaces of the metals to be soldered, allowing the solder to properly wet and adhere to the surfaces.
—— snip ——

Cheers,
-jonny