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How concentrated should I make a citric acid pickle ?

Neutralising the flux after hard soldering.

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IanT20/12/2015 10:08:47
2147 forum posts
222 photos

I use citric acid to remove soldering and brazing flux and (to some extent) scale & rust from bits.

I've never worried too much about "how much" - the main problem (in practice) is to be able to cover the part if it is large or awkwardly shaped. For these parts I first find a suitable (e.g. not too big) container - I have a few different shaped/sized ones (an old plastic bowl, ice cream containers, cut down milk bottles and a old home brew 'tub'  ) and fill it with hot water just sufficient to cover the part. Dependent on the amount of water used (which I simply guess), I put in about a heaped teaspoon per pint.

I then fish the part out after an hour or so and give it a bit of a scrub with wire wool and/or pick at any flux with a 'scratcher' (depends to some extent on the existing state of finish). Sometimes this is sufficient but usually it needs more time in the solution - but I keep checking fairly regularly and scrubbing/picking at the worst of the flux. So to my mind a fairly dilute solution works fine but what you must to do is monitor the part for progress and not leave it in over long. Having said that, I will often leave rusty steel parts in solution overnight - it's the non-ferrous stuff I watch more closely

I used to buy small packets of citric acid (50-75gms) from chemists but then discovered that for just a bit more I could get 1kg bags from eBay (look for Citric Acid & Indian Cooking). I use old plastic milk bottles to keep & store used citric solution and it seems to work fine (any 'muck' settles to the bottom) if I pour off the clear part of the solution and then top it up & cover the part with hot new solution... . Not too much science I'm afraid but it seems to work for me.

Hope this helps.

Regards,

 

IanT

Edited By IanT on 20/12/2015 10:09:18

Ian S C20/12/2015 11:25:29
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7468 forum posts
230 photos

Also look at Home Brew Shops. I use a bit stronger, about one desert spoon per litre.

Ian S C

mechman4820/12/2015 11:43:47
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2947 forum posts
468 photos

Thanks for info' IanT & Ian SC

Have wondered abut this aspect for a while; have a couple of packets of Citric Acid from home brew shop for future use, now I have some idea of ratio.

George.

Brian Abbott21/12/2015 23:04:01
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523 forum posts
95 photos

Thanks all for taking the time to reply,

not had chance to try the suggested mix but hopefully will do over Christmas,

Gordon French 122/12/2015 00:17:21
4 forum posts

I have found that I can store my pickle in picnic cooler chests. I also store me welch steam coal under water

in another one. If you need clear water in large quantity you can use these chests to collect rain water.

with a trash can liner for a funnel.

Gordon French

Roseburg, Oregon USA

Peter Etherington 226/08/2021 17:56:44
26 forum posts
1 photos

Cup alloys suggest a mix of 20g of salts to 1 litre of water

Jon Lawes26/08/2021 18:04:05
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1078 forum posts
Posted by Peter Etherington 2 on 26/08/2021 17:56:44:

Cup alloys suggest a mix of 20g of salts to 1 litre of water

I suspect at six years old he has probably come up with a solution... pun intended! wink

Dave Smith 1426/08/2021 18:20:18
222 forum posts
48 photos

I bought a 5kg bucket of it from Ebay for about £10.

Bob Stevenson26/08/2021 18:48:41
579 forum posts
7 photos

Interesting topic!......

I do have some citric acid.......the remains of a small pack that came from Cup-Alloys and a larger bag from a brewing supplies outlet. It's not expensive, is safe for humans and is easy enough to use.....

However, I have stopped using it now as I did'nt really like how it treated my clock parts. Citric quickly turns brass parts a distinct pink colour, presumably by removeing the surface zinc so that copper is uncovered and also b y giving the surface finish a 'satin' or semi-matt effect. All these symptoms show up quite quickly.

I now just wash and lightly scrub brass parts in ordinary household detergent in hot water and use a soft nylon nail brush. So far I have not seen any problems with flux etc being retained around joints and will go on using it instead of citric....although there may well be a chance of using the unique look of citric on a future clock.

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