Going to you tube to learn about soldering i see different people suggest readily available house hold products for use prior to soldering. Namely: Alcohol (or surgical spirit), lemon, toilet lime scale remover or vinegar. Which is the best bet ?
What are you going to solder? I would definitely avoid toilet cleaner - they are not all the same. I have never used lemon or vinegar for any soldering that I've done in the past 50 years (electronics and plumbing)
Copper pipes you use an abrasive to clean the surface - emery cloth or wire brushes designed to fit inside or around the outside of the pipe.
Home made printed circuit boards - again a mild abrasive - green washing up scouring pads for instance.
If you are just cleaning up a few pads on a commercially produced board you can get pens with an abrasive tip.
If a printed circuit board is already tinned then apply fresh solder with a integral flux or use a liquid flux. It depends on what you are trying to solder. The techniques for surface mount components are somewhat different to soldering discrete components.
In general, freshly stripped wire should not require cleaning.
After soldering a stiff brush and IPA can be used to clean off excess flux. IPA in a aerosol can is possible the easiest to use
I have yet to find a way to solder stripped wire, where the wire has gone black.
I find that scraping back to bright copper as best you can, add flux and leave for a bit, then solder. Just about works, although not as easy flowing as with clean copper.
Avoid surgical spirit. It contains castor oil, which leaves a greasy residue. Similarly, you don't know what else is in the toilet lime scale remover, so avoid that.
Otherwise, it depends what you want to solder and what you need to clean off. As others have said, mild abrasion works best at removing surface oxidation. Alcohol is good at removing grease. Isopropanol is readily available for cleaning computer screens, so would be a good choice. Methylated spirits again contain additives you don't really want, unless you have a licence to buy industrial meths.
Citric acid based cleaners also work well, although I don't know about its raw form (lemon juice). Vinegar I wouldn't have thought of as the acetic acid is well diluted, but if you try it, use white, not malt or balsamic.
Acid plumbing flux can work but possibly not recommended as capillary action could/will take it up under the insulation. Ideally you need to completely clean this off before soldering.
In my experience if you have heavily oxidised wire just chuck it out. It's too much hassle to get reliable results.
Also, "methylated spirits" means different things to different people. I think of it as the dyed-purple alcohol that is sold under that name, but some people (maybe Americans) take it to mean what we call "surgical spirit" - an alcohol scented with oil of wintergreen. Probably the same base alcohol but different additives to denature it and make it "undrinkable" (for some value of "undrinkable" depending on how desperate you are!).
What kind of soldering - electronic or plumbing?
For electronic soldering the key ingredient is flux: it breaks down the oxide layers that form and allow solder to flow. It works like a wetting agent that turns solder from substance that forms balls on the end of your iron to one that flows along copper surfaces - it's a bit like the difference between plain water droplets and water with washing up liquid in it. It's critical for surface mount soldering.
If the item is very corroded, some mechanical abrasion is useful, but otherwise flux is the thing to use - some of the other chemicals will actually corrode the copper and make things worse. You can get flux in liquid form, eg in a pen dispenser, in gloopy form in a syringe or tub, or in paste mixed with solder. Most solder wire is flux-cored but often extra flux makes things flow better.
For plumbing flux is important too, but I would start with a good mechanical clean. I'm not sure if plumber's flux is safer around drinking water than the electronic kind.
Make sure you clean the flux off afterwards - as flux is corrosive it can eat away at your copper if it stays around. You can get water soluble fluxes which mean you can wash your PCB, or otherwise IPA or acetone are good for washing traditional rosin flux.
Theo
There are/were different types of plumbing flux. I believe the aggressive acid flux is banned on gas pipes as it cannot be cleaned off the inside of the pipe and may/will continue to corrode the pipe. It may now also be banned from water intended for drinking but the flow of water inside the pipe will eventually wash it away.
The aggressive acid flux is very good for cleaning the copper but I've found in the past that the very fine surface pitting it created made subsequent dry fitting a PITA. Dry position fitting to a pipe and the friction between the two mating surfaces made it almost impossible to pull apart again. Much better to abrasively clean the surfaces and use a acid free flux.
What sort of soldering? Soft solder or something more interesting?
If you are going to use an acid cleaner then my money would be on HCl and then rinse with distilled water and dry. None of the things you have suggested is really pure enough to clean parts to be soldered reliably.
I find 600 grit carborundum paper the ideal method for cleaning parts to be soldered coupled with whichever flux is appropriate for the solder.
Most electronics is done with self fluxing solder these days. It used to be a lead based solder but not any more. You need to keep the two quite separate as they do not mix well.
I would add that rework flux is extremely useful, and not just for surface-mount. There are times when geometry requires the commission of that ultimate soldering sin, carrying solder on the tip to the joint. That can often be done successfully with a dab of rework flux on the joint first.
I've used Electrolube SMFL for many years but it now appears to be discontinued, presumably because it was good. I suppose when I run out I'll have to try something random from Ebay.
wire wool.
no bad thing, since there is no knowing how far the corrosion has gone. But I think plumbers flux will do it
They have SMF in liquid pen form:
but I've always found the gel fluxes to work better - they have a gloopiness that means they stay put, whereas the liquid form would tend to spread (and an aerosol seems like a awful dispensing method unless you're preparing large copper sheets). The syringe dispensers are good for applying them in small quantities.
Theo
I actually spray the stuff into an old lens cap, where the solvent evaporates. I top up with a drop of IPA when it gets too solid.
It sounds like you're trying to make your own gel - I'd recommend trying one of the ready made ones.
Theo
Methylated spirits simply means ethanol with enough methanol (c10% IIRC) mixed in to make it poisonous. With a licence, you can buy industrial methylated spirits which is completely clear and is just those two alcohols mixed, with no additives.
Not quite. I just looked up the regulations which are remarkably complex. Well worth a look!
John
I might, had you provided a link.
I'd be a very wary with acetone on electronic circuits, especially when there are small plastic connectors or switches. Acetone can melt some plastics. With some plastics you can dissolve them in acetone to produce a thick type of glue similar to that used on Airfix model kits.
On the subject of solvents I once destroyed a rs232 socket by trying to loctite the mating half for the locking (jack) screws and got some of the loctite on the plastic bits. No obvious immediate problem but when I tried to mate the plug a day later and found the plastic bits a bit like a very viscous jelly :(
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