# Acid flux ?



## purpleknif (Feb 3, 2014)

I'm working on a Liney 5 and  need to do some soldering of brass parts. Some of the features involved are kinda small so I'm wondering how to get them clean enough to solder well, Back in the day they used to sell acid flux in just about any hardware store. Not any more. What can I use instead? Or just get some sulfuric acid and mix up a weak batch ?

  Thanks


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## lennardhme (Feb 3, 2014)

Tablespoon of citric acid [avail. homebrew or supermarket shops] in a litre of cold water. 
Leave for @ 4 hrs or until clean. Rub with new kitchen scourer. Dont touch.
Safe
Seal in a plastic container 7 will last for a year or more - but will form an unhealthy looking sludge, but still quite safe.
Also extra good for copper boilers etc.
Leonard


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## goldstar31 (Feb 3, 2014)

Frankly, I would not bother with sulphuric acid and all the attendant dangers of diluting from concentrated H2 SO4  and think of simpler solutions. If it was just a bit of brass, I would probably rip out a bit of zinc chloride from a dry cell battery.  I would probably dunk the bit of brass in a bit of vinegar or even Brown Sauce- both of which contain acetic acid which is far more gentle. Maybe citric acid crystals would suffice. Some of the Brit boiler folks swear by them- but I have no experience personally. Again, if larger quantities were needed I would use something like a pre-clean for car body work which probably contains a mixture of hydrochloric acid and phosphoric acid.   
 Once you have a clinically clean surface, you can use a variety of fluxes. There are the resin cored solders but you could get away with nothing more than tallow. I used tallow as a boy to mend lead piping bursts and this, given the right solder, it will fill and wipe with fustian cloth. 

 Personally, I like solder pastes both lead/tin and silver. But that is just me. Presently, I am doing a lot of wiring and a lot of the cables are satellite and ordinary tv cables which have been outside in the snows, rain and assorted atmospheric pollution under trees and so on. Quite often I merely use a pruning knife scrape of the corrosion before tinning again. 

 Does this help?


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## Steve J (Feb 3, 2014)

just go to the local hardware and get paste flux for copper pipe. works well on copper brass and steel or combinations of all three


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## BaronJ (Feb 4, 2014)

Plain vinegar is all I use.  For small stuff, a cotton bud dipped into it as needed.
You can see the surface change as you wipe it.

I've used ferric chloride before now but its nasty stuff, more usually used for etching the copper when making printed circuit boards.


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## purpleknif (Feb 4, 2014)

Was thinkin about vinegar. Didn't know if it would work.

 Thanks.


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## OrangeAlpine (Feb 5, 2014)

Why acid flux?  I have it, but seldom if ever use the stuff.  I've found that if the material is cleaned, resin flux works very well and I don't have the corrosive material to deal with.  In general, if the resin flux does not work, neither will the acid.  

What I have found is that there is a world of difference in solders.  some of it is impossible to used for anything but fishing weights.  Specifically, Oatey solder.  Got a spool of it a few years ago, would bead up like water on a freshly waxed car.  That was using resin flux.  I was somewhat surprised that I was suddenly have problems soldering.  So I bought the acid flux.  Made absolutely no difference.  I bought another brand of solder (Bow).  The problem went away, I returned to using resin flux and the Oatey solder went into the trash.  

Problem solved.

Bill


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## BaronJ (Feb 5, 2014)

OrangeAlpine said:


> Why acid flux?  I have it, but seldom if ever use the stuff.  I've found that if the material is cleaned, resin flux works very well and I don't have the corrosive material to deal with.  In general, if the resin flux does not work, neither will the acid.



Hi Bill,
The only disadvantage with "Resin/Rosin" fluxes is cleaning the residue off.



> What I have found is that there is a world of difference in solders.  some of it is impossible to used for anything but fishing weights.  Specifically, Oatey solder.  Got a spool of it a few years ago, would bead up like water on a freshly waxed car.  That was using resin flux.  I was somewhat surprised that I was suddenly have problems soldering.  So I bought the acid flux.  Made absolutely no difference.  I bought another brand of solder (Bow).  The problem went away, I returned to using resin flux and the Oatey solder went into the trash.
> 
> Problem solved.
> 
> Bill


I don't know of "Oatey" solder but I've had few issues with wetting.  More often than not surface contamination is the cause of balling.  Hair lacquer being one.  I agree some lead compounds are more suitable for making cast soldiers !


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## OrangeAlpine (Feb 5, 2014)

The good part about resin flux is the stuff is not corrosive and very safe to use.   It washes off quite nicely with isopropyl alcohol.  

My problem had nothing to do with surface contamination.  A change of solder and the problem was gone.  The appearance and disappearance of problem was very dramatic.  I was midway through the job when my old solder (Kester) was used up.  Bought the Oatey solder and BAM!  Couldn't solder.  Different brand and the problem disappeared.  And I have NEVER used hair spray;D  

I suddenly understood why some guys have trouble soldering, as Oatey is a very prominent brand.

Bill


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## goldstar31 (Feb 6, 2014)

OrangeAlpine said:


> Really, most of the problem is not having the right lead/tin/cadmium/silver--whatever compound rather the name on the stick.
> 
> Too long a subject for  a discussion here but 'Wiki- whatsit' will give some idea.
> 
> ...


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## abby (Feb 6, 2014)

Search for Bakers fluid on ebay or you can make your own by adding zinc foil or sheet to hydrochloric acid until it no longer dissolves (killed spirits).
This is the traditional flux used in the trade by coppersmiths and tinsmiths for centuries using both an iron or direct heat. 
I use nothing else for soft solder , it works really well but beware , it will release enough acid into the air to turn tools rusty overnight and will cause verdigris on brass or copper if not rinsed off well ,for this reason I would not recommend its use for soldering electrical cables , the rosin based fluxes such as fluxite or cored solder are best suited to cable work.


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## OrangeAlpine (Feb 6, 2014)

goldstar31 said:


> Really, most of the problem is not having the right lead/tin/cadmium/silver--whatever compound rather the name on the stick.
> 
> Too long a subject for  a discussion here but 'Wiki- whatsit' will give some idea.
> 
> ...


You are right.  Oatey is a supplier of plumbing materials in the USA.  The problem is that in a lot of hardware stores it is the only brand available and most guys think (as I did) that solder is solder and any brand will do.  

My apologies, I forgot about the international nature of the board's readership.

Bill


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## purpleknif (Feb 6, 2014)

Lots of good information here. 
 Thanks. Yes there is a world of difference in solders. I used to solder a lot of R/C battery packs for racing. As you can imagine a quality joint is critical. I found the best solder to use was good ol' Radio Shack. Results were visible on a discharge cycle.


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## chucketn (Feb 6, 2014)

purpleknif said:


> I'm working on a Liney 5 and need to do some soldering of brass parts. Some of the features involved are kinda small so I'm wondering how to get them clean enough to solder well, Back in the day they used to sell acid flux in just about any hardware store. Not any more. What can I use instead? Or just get some sulfuric acid and mix up a weak batch ?
> 
> Thanks


 
If you have a Fastemal close, they carry an acid flux for $12 and change.

Chuck


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## barnesrickw (Feb 6, 2014)

Fastenal is a pretty cool toy store.  Got some drill rod and another 4-40 tap today.  So much more I wish to buy.  


Sent from my iPad using Model Engines


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## goldstar31 (Feb 7, 2014)

May I go back to where my small contribution ended? None have raised the points and I think that they will be useful. 

 The first is solder paste. Now it is available because I took time to establish that there was something in the USA that was comparable with my old tutor's book 'The Repair of Vehicle Bodies'. I see that Alan's original lecture notes have been made into  several editions - now with a Mr Livesey co-authoring. It's in pdf. One of our competences was to take damaged car panels( they were donated by Nissan), hack them about, stick them together, but finally have them as new- or better , ready for the spray shop. So they were high strength, low alloy steel with niobium in. Yer can't put too much heat in that stuff but if you are careful, you can tin with solder paste before sticking body solder on like putty- you know with a wooden paddle and cooking oil. So Alan, in his best University tie and Sunday meeting suit lit up a soft flame of oxy/acetylene and smeared the work with solder paste. He watched carefully until the little globules of solder appeared under the flux- and immediately rubbed the work with a tissue handkerchief so that it was fully covered and the rest rubbed off. Time for the body solder which he put on using the torch itself as the tool. And that is how the experts do it!

 The next trick is from - my wife- who is no mean wire bender, welder and silver solderer.  To keep the solder in place, she always used a line defined by a HB or softer lead pencil to keep the solder where it was needed.  It works.

 So get a little tin of solder paste- which has a very high tin content.


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## pkastagehand (Feb 7, 2014)

goldstar31 said:


> The first is solder paste. Now it is available because I took time to establish that there was something in the USA that was comparable with my old tutor's book 'The Repair of Vehicle Bodies'.



Just a quick google search for "solder paste" does indeed get a lot of hits.  Most of them seem to be about surface mount electronics soldering.  More info of composition or a brand, etc. would be much more helpful than merely saying soldering paste.

Paul


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## goldstar31 (Feb 7, 2014)

I would go into a rather a supplier of proper motor vehicle suppliers rather than the little guy who sells 'Bonda -something' and ask them. Alternatively, decent suppliers of stuff for silver soldering will come up with knowing that two pastes are used. The first is powdered silver whilst the other is powdered tin both in an acid etch/cleaning flux. 

 Actually before commenting, I looked for Alan Robinson's book on the 'net and found that there was a comparable reference book on the 'net on motor vehicle restoration which includes the use of solder pastes -but in the US. 

 So I hope that you be successful in your search.

 Meantime, thank you for your question.

 Norman


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## BaronJ (Feb 7, 2014)

pkastagehand said:


> Just a quick google search for "solder paste" does indeed get a lot of hits.  Most of them seem to be about surface mount electronics soldering.  More info of composition or a brand, etc. would be much more helpful than merely saying soldering paste.
> 
> Paul



Hi Paul,
Yes I have a couple of 50 Grm syringes of that stuff !  Its dammed expensive and has a limited shelf life.  I wouldn't have thought to use it like normal solder.  But its great for SM components.


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## purpleknif (Feb 7, 2014)

I drive right in front of a Fastenal every day on my way to and from work. I'll give them a try. I've found them rather pricey on most items compared to the Production Tool Supply about a ten minute drive away. But,,, when you need it today...


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## goldstar31 (Feb 7, 2014)

Fryolux- a lead solder paint is £40 for 500 grams( just over 1pound weight) at trade factors like Cromwell Tools and very much less on E-bay. Perhaps the confusion lies in whether the paste is silver- for such purposes as jewellery or medical/dental applications or making boilers for model  locomotives. 


 Cheers

 Norman


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## KLG (Feb 12, 2014)

In OZ the standard flux used to be called Bakers soldering flux and it was great on tinware, galvanised sheet and brass and copper.
I can be made by taking some hydrochloric acid(swimming pool) and throwing in a handfull of galvanised nails. You end up with a zinc chloride solution. Use plenty of nails so that the acid is effectively killed. Also called killed sprits of salts.
Cheers,
Kerry from OZ


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## BaronJ (Feb 12, 2014)

KLG said:


> In OZ the standard flux used to be called Bakers soldering flux and it was great on tinware, galvanised sheet and brass and copper.
> I can be made by taking some hydrochloric acid(swimming pool) and throwing in a handfull of galvanised nails. You end up with a zinc chloride solution. Use plenty of nails so that the acid is effectively killed. Also called killed sprits of salts.
> Cheers,
> Kerry from OZ



Hi Kerry,
Its called that here too !  Not that I have seen any for sale recently.


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## purpleknif (Feb 13, 2014)

Lots of options here. I should find something that will work. Thanks guts. Now if the weather would warm up so I could do some work...


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## ChipsNChips (May 22, 2014)

There are many varieties of rosin flux and I use it all the time. First, there is no need to remove it except for appearance sake. Second, yes alcohol does work but most electronic supply places sell spray cans of flux remover which works even better and faster. I use an old tooth brush with either of them to scrub the flux off. 

One caution: the solvent will carry the flux into any areas where it can penetrate. I have had fits with circuit boards where the flux was carried into switches and relays and built up an insulating layer on the contacts. I had to wash them down with a lot more solvent to wash it out. This is probably less of a problem with mechanical assemblies, but I can see where some parts would be adversely effected. So watch where the solvent/flux mixture flows to. 



OrangeAlpine said:


> The good part about resin flux is the stuff is not corrosive and very safe to use.   It washes off quite nicely with isopropyl alcohol.
> 
> ...<snip>...
> 
> Bill


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