Removing Flux

This topic has 11 replies, 9 voices, and was last updated 2 May 2019 at 15:27 by Former Member.

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2 May 2019 at 10:31 #407459
Paul Lousick
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@paullousick59116
What is good for removing flux on copper, bronze or brass after silver soldering ?

Paul
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2 May 2019 at 10:31 #26588
Paul Lousick
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@paullousick59116
2 May 2019 at 10:43 #407462
Thor 🇳🇴
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@thor
Hi Paul,

Diluted sulphuric acid is often used for pickling, but must be handled carefully. I now use citric acid in warm water.

Thor
2 May 2019 at 10:44 #407463
mechman48
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@mechman48
I have used citric acid, from the home brew counter in a well known discount store, vinegar also works well.

George.
2 May 2019 at 10:44 #407464
Former Member
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@formermember19781
[This posting has been removed]
2 May 2019 at 10:48 #407465
Simon Collier
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@simoncollier74340
Is this a trick question Paul? The obvious answer is sulphuric acid. A friend recently found 1 litre bottles of concentrated H2SO4 in a cleaning supply shop. Cheap too. The plastic bottles are weirdly heavy too, reflecting the concentration of relatively heavy sulphate ions. I use it at 2 molar (roughly 1:10) but that is overkill.
2 May 2019 at 12:09 #407473
Paul Lousick
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@paullousick59116
No trick Simon. I have done a lot of welding and brazing but have not pickled the metal to clean. (My search of previous posts did not come up with anything). Will give the citric acid a go first to see if it works.

I have used typist's correcting fluid to mask the metal where I did not want the solder to flow. This worked but is there a better method ?

Cheers, Paul.

Edited By Paul Lousick on 02/05/2019 12:13:13
2 May 2019 at 12:14 #407474
Simon Williams 3
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@simonwilliams3
Hi Paul, this comes up every so often, and the perceived wisdom seems to be brick cleaner from your local builders merchant. I've tried it and it works a treat. Buy the one that actually says it contains citric acid, other formulations exist.

Good luck Simon
2 May 2019 at 12:30 #407475
Nick Clarke 3
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@nickclarke3
Most acid based brick cleaners appear to be based upon 10%-18% Hydrochloric Acid (sometimes otherwise described as Hydrogen Chloride)

Citric Acid is often cheaper when bought from a shop selling homebrew ingredients.
2 May 2019 at 14:37 #407493
BW
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@bw
Baking section at Tescos, Sainsburys, Woolworths, Foodland, Safeway etc etc will usually have citric acid in powder form. Quite cheap.
2 May 2019 at 14:49 #407494
Samsaranda
Participant
@samsaranda
Cheaper source of Citric Acid is the internet, food grade available at very reasonable cost, much less than supermarket prices. Citric Acid works well for me and I wouldn’t contemplate using Sulphuric or Hydrochloric, way too dangerous, Citric takes longer to achieve the same results but we are not working in industry tied to production schedules so a bit extra time doesn’t matter.

Dave W
2 May 2019 at 15:27 #407499
Former Member
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@formermember19781
[This posting has been removed]
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