Posted on 03/14/2024 3:00:58 PM PDT by Paul R.
Is the inside surface of clear copper tubing, such as used in refrigeration systems, anodized or have some other finish applied to it? It appears to be impossible to solder to, even using acid flux, unless the surface is thoroughly sanded (or use steel wool or a wire brush). The inside surface "as is" looks clean, with no darkening or oxidation, but is smooth, lacking the tiny scratches of sanding with high grit sandpaper, or using steel wool on it.
The tubing is brand new.
Thanks!
Good paste Flux, old school tin/lead solder. Some 400 wet / dry 3M emory cloth.
Why are you trying to solder inside the pipe? Soldering works by capillary action.
This should help: https://youtu.be/TYj4uJjaP8g?si=NeqX0fK9sTHI4vIW
Try using a brazing rod with the material.
Nothing that I know of, although it certainly has an oxidation layer that has to be cleared (obviously).
One thing I learned the hard way, having worked in ‘the business’ a while ago, is to be absolutely sure that the flux you use is fresh, as in recently purchased at a high-volume outlet, as using old flux is not any different than using no flux at all.
Copper is quite easy to sweat. The surfaces must be clean, steel wool works great, so does fine emery cloth. A good flux and plenty of heat, preferably MAP gas.
Heat the joint uniformly. When hot touch the solder to it, when it begins to flow it should suck right into the joint, all the way around. Push the solder into the joint as it flows and stop after the first drip on the bottom.
A good plumber does not wait for the first drip to stop, but can tell when the joint is full by the silver ring that develops all the way around.
Trust me.
To get solder to take easily & quickly, use a cylindrical stainless wire brush inside the tube.
Are you building a still?
Well, that's what doesn't work, unless I sand off the finish on the inside surface. That is a bit difficult to do well, unless I open the "u" further (it's closer to a "C", really), sand it, then bend it back to the shape I need. The pieces are small enough to be a bit hard to hold on to while sanding. Possibly a small wire brush attachment on my Dremel tool would work better than trying to sand by hand. But, I'm just puzzled / curious as to the problem. I've done a lot of copper pipe soldering in the past, but that was to the outside surface of the pipe or tube, slipping into some fitting. Never had a problem with the inside surface of a fitting, if new. Anodizing the inside surface of the tube WOULD sort of make sense to extend its lifetime. Or maybe this is oxidation, but not to the point of darkening or "greening" the copper? This looks very "even" though - not "patchy" at all.
Must use good Flux!! Sand with good emery cloth.
C-Flux
“”””One thing I learned the hard way, having worked in ‘the business’ a while ago, is to be absolutely sure that the flux you use is fresh, as in recently purchased at a high-volume outlet, as using old flux is not any different than using no flux at all.””””
I’ve used old flux kept in my plumbing van for years in a hot climate and never had a problem.
Being a repair plumber, my can of flux with the hole in the lid and a brush sticking out would be used for years and the old backup cans that had been stored in the van for years then being opened.
Yup, long as drinking water will never pass through it old lead solder can be easier to work with.
Copper is a fantastic conductor of both heat and electricity.
It makes it hard sometimes to get the copper hot enough to
let the solder adhere though... a torch is usually needed to
get the temp up... and lots of flux.
Silver is even better as a conductor of heat and electricity
and if it was as plentiful as copper would be used instead
in many applications. I have seen silver heatsinks used on
certain critical hardware... I will have to stick to aluminum...lol
The treasury sent the military most of its silver in WW2 for wiring used in the Manhattan project.
Could be the brand I attempted to use at the time. I finally tried another can, but much newer, then no problem.
“unless the surface is thoroughly sanded (or use steel wool or a wire brush)”
Maybe because of oxidation or formation of some microscopic coating on the copper, it has to be sanded or abraded before solder will attach. Also could be that the sanding creates an abraded / non-smooth surface that makes it easier for the solder to attach to the copper. Just sand it.
Use the old lead containing solder; the new lead free stuff isn’t as fluid and doesn’t it wet the surfaces as well. Also make sure your torch has a large enough flame. I use a prestolite air/acetylene when doing copper typing. Also no matter how clean it looks don’t skip the sanding and steel wool step and don’t skimp on the flux.
Or alternatively if you have oxy-acetylene you can braze it that way you can just build a fillet around the outside of the joint, but I find brazing a lot harder to get a nice looking result - probably because I only do it rarely.
If you can get nitric acid a 25% solution will clean it very quickly but be sure to rinse it really well
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