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Cleaning up after Silver soldering (brazing)

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Clive12/11/2010 01:02:18
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4 forum posts
Hi all, I need some advise about cleaning the work after silver soldering.
 
I have made an exhaust for a 35cc glow engine from brass and copper. I step soldered the job using easyflow2 flux and tenacity flux.
 
I now need to clean of the flux residue and charring that wont come of with warm water and brushing.
 
Someone said I need to pickle it? Can someone explain what this is and where I get it from?
 
Clive
 
 

Sam Stones12/11/2010 04:35:28
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922 forum posts
332 photos
Hi Clive,
 
My limited experience about silver soldering, although not about pickling, is as follows :-
 
I have only used borax as a flux, which forms into a glass-like coating during the silver soldering process. The best way of removing this, is to immediately plunge the item into boiling water while it is still hot from soldering.
 
If the item has already cooled down, then you might consider reheating it and having some boiling water ready to hand.
 
It has worked for me before, so this might work for you.
 
I'm not sure about the charring you mentioned, which is (perhaps) where the pickling comes in.
 
Ask the model boiler makers!
 
Regards,
 
Sam

Edited By Sam Stones on 12/11/2010 04:36:33

Richard Parsons12/11/2010 04:36:05
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645 forum posts
33 photos
 

Pickle

Pickle is an acidic liquid which dissolves away the flux and the fire scale. You can use (if you can get it) dilute sulphuric acid. You can use a solution of sodium Bisulphate (NaHSO4) again if they will let you have it. You can also use Citric acid but it is much slower than the other two above and is not as good with fire scale.

Over here in Hungary I use 10% acetic acid (white vinegar)

When diluting an Acid (or anything else) ALWAYS add the acid to the water Never the other way round.

Bogstandard12/11/2010 04:58:21
263 forum posts
Clive,
 
For a perfectly safe pickling solution, go to either a chemist or a home brew shop and purchase some citric acid. It comes as crystal and is perfectly safe to handle.
 
Get yourself a small plastic container with a lid, big enough to put the parts in and fully immerse them.
 
2/3rds fill the container with warm to hot water, and spoon in the granules whilst continually stirring, don't put too much in at a time. Keep slowly adding the crystals until no more will dissolve in the solution. Thats it, you have a saturated citric acid pickling mix.
 
A small box from the chemists will cost around £1 or a bagfull from the home brew shop maybe a couple of squid. The small box will make about 4 pints of pickle. Some supermarkets stock it in their cooking departments. The chemist might ask you what you are going to use it for, as it is sometimes used for processing certain illegal drugs, so just tell them the truth.
 
Put your bits in and wait for an hour, and you should find that things have really cleaned up. If not fully cleaned, just put the bits in a little longer, they can stay in there almost indefinitely withou coming to harm.
 
Don't throw the mix away, it can be used over and over, until it starts to lose it's cleaning power.
 
You can add a teaspoon of domestic bleach, that will keep the fungus growth down over long periods of storage.
 
I use mine until it is almost black, and as long as what is growing in there hasn't got tentacles, I class it as safe to use.
 
You can use stronger pickling salts  or even diluted nasty acid mixes, but this one is cheap and SAFE.
 
 
Bogs
 

Terryd12/11/2010 06:47:30
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1946 forum posts
179 photos
Hi Clive,
 
I fully endorse Bogs method of pickling.  It is reasonably fast as well as safe.  We used to use 20% Sulphuric acid but i| much prefer to use citric now and it gives good results.
 
Terry
keithmart12/11/2010 07:57:29
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165 forum posts

Hi


I have found that ordinary malt vinegar works well as a pickle with brass and copper.


It is cheap, and you can get it in gallon bottles from your local supermarket.


I would NOT advise using it on your chips afterwards though!!!!


Regards


Keith


Leeds UK

Chris Trice12/11/2010 08:22:25
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1376 forum posts
10 photos
To get a nice finish after pickling, scouring the part with an abrasive pad of the type used to denib paint gives a clean bright look. Given how hot your exhaust manifold is likely to get, it will probably tarnish again pretty quickly though even in the oily enviroment.
Clive12/11/2010 08:28:48
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4 forum posts
Thanks to all for your replys.
 
I now understand and am off to get the required "ingredients". 
 
What a brilliant forum, all these replies in under 7 hours!
 
Clive
Gordon W12/11/2010 09:56:19
2011 forum posts
I am quite new to silver soldering, all the above methods work. But stuck in the middle of nowhere I didn't have any of the above, so boiled my new small boiler in a pan of water with a hand full of washing powder (machine wash stuff), then rinsed well, it came out very clean, and no corrosion a year later.
KWIL12/11/2010 11:26:04
3681 forum posts
70 photos
Domestic drain cleaner [liquid], well diluted. It is acid, use rubber gloves and rinse well. Observe frequently.
Terryd12/11/2010 14:26:25
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1946 forum posts
179 photos
Hi there,
 
Here is an example of a barrel I made for a small boiler.  It was made from flat sheet using a silver soldered grooved seam joint for strength.   It was placed into the citric acid solution while warm and took about 10 minutes to get to this state.
 

50mm dia boiler barrel silver soldered
 

 
 

Hook or grooved seamed joint
Clive12/11/2010 22:50:12
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4 forum posts
Well, I did the rounds of various local stores to try and find the ingredients but failed, so I phoned Chronos who had some pickling salts in stock. So, after a short drive and one hour later I had the work in the pickle bath and hey presto a lovely clean exhaust x2.
 
Brilliant, and thanks to all for your help.
 
 Clive

clive swinney13/11/2010 12:28:46
6 forum posts
I read recently on the web that kettle descaler can be used for pickling. Has anyone tried this and does it work
Bruce Voelkerding13/11/2010 13:05:45
77 forum posts
7 photos
a couple of questions regarding Terryd's boiler:
 
o would one put flux in the joint before finishing the final bend or just flux the inside & outside before silver soldering ? Is it necessary to have flux between two parts (in the .002" gap for the silver solder) or just around the egdes ? A case in point - a Foundation Ring on a locomotive bolier - I could see that taking me all day to fit and rivet up. Silver Soldering might be the following day or weekend. When/where do I flux ?
 
o  can one flux up an assembly a day before silver soldering or should one flux just before xilver soldering ?
 
Bruce
KWIL13/11/2010 16:04:30
3681 forum posts
70 photos
All surfaces that are to be silver soldered must be fluxed, even inside the joint so that the solder has a clean face to bond with. 
 
Why rivet the Foundation Ring? Hold in position with unclosed rivets and allow the silver solder to flow through the joint properly, if you close the rivets there will be areas that are closer [ ie closer than 0.002"-0.004"] than the solder can penetrate and you could end up relying upon the external fillet to seal the joint which is not good practice.
 
Freshly fluxed every time.
Terryd13/11/2010 17:24:10
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1946 forum posts
179 photos
Hi Bruce,
 
Theoretically the flux should chemically scour the oxides from the metal as you solder once the alloying process begins, so the flux and solder should run through the joint even if you don't flux between the metal.  However in practice I flux between the joint before assembly and then apply a thin film of flux to each side of the joint just before final soldering.  That will allow you do do a final clean up to remove any oxides which have formed overnight and ensure a complete soldered joint.
 
You could always give the assembly a pickle in acid just before fluxing to ensure absolute cleanliness. I was taught by an old silversmith who could sequence 4 or 5 joints in a complex piece and simply used borax for his flux at all temperatures.
 
 Terry
John Olsen14/11/2010 18:44:40
1294 forum posts
108 photos
1 articles
I've just been doing some small eccentric straps, these are made on a jig with a brass fork for the top, a two piece brass eccentric strap for the bottom, and a 1/8 inch steel round bar with two slight bends in between, to give the offset to line up with the link. These turn out to be more challenging to silver braze nicely than I expected. The top joint is not a problem, but with the bottom one it is hard to get the relatively large area of brass hot enough before the steel is overheating the flux on it.  The jig is acting as a heat sink for the brass part. So I find that the way to do it is to use the oxyacetylene, since the narrow flame enables me to direct the heat where needed. Of course a softish flame is used, and the torch is kept well away, since accidently melting brass bits is the easiest thing in the world to do. An alternative that I have not tried might be to use a much larger propane torch and heat the whole jig up to near red heat from the other side first.
 
regards
John
Stub Mandrel14/11/2010 20:38:34
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4318 forum posts
291 photos
1 articles
I use a sulphamic acid based limescale remover from Aldi, but almost any organic acid will do the job. Ciric has the advantage of being very clean and low toxicity.
 
I can't see any rational reason for using sulphuric acid pickle.
 
Neil
Michael Kilpatrick 117/12/2010 16:27:19
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10 forum posts
Once Upon aTime i worked in the shipyard as a relaxee Coppersmith.
Silver soldering was carried out using esyflo paste/powder the soldered item was soaked for a minimum of one hour in a huge heated tank of water. if the pipe ect could not fit in the tank it got a minimum of 24 hours cold soak. 
Pickling OTT
Regards
Mike
macmarch17/12/2010 16:55:45
147 forum posts
1 photos
I purchased a bin that is intended to contain bird seed and the like. It comes with a clip on lid. My one is about 5 gallon capacity. put in 3 gallons water and a LOT of Citric acid.
Let your brazed/silver soldered joint cool for a couple of minutes then plunge in and leave until clean. Just be careful that the solution doesn't rush up any tubes etc.
 
 
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