Neutralising Bakers No. 3 fluid

Neutralising Bakers No. 3 fluid

This topic has 5 replies, 5 voices, and was last updated 27 June 2026 at 18:27 by Pippin.

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27 June 2026 at 13:07 #853693
Pippin
Participant
@phillspowart84010
Did some soldering of mild steel, using Bakers No. 3 as a flux. 3 weeks later, and anything that went near the job won’t stop rusting. Have scrubbed with scotchbrite and evaporust then oiled up, just goes orange again. How on earth do I stop it?
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27 June 2026 at 13:20 #853699
JasonB
Moderator
@jasonb
Bicarbonate of soda mixed with water.
27 June 2026 at 13:21 #853700
Neil Wyatt
Moderator
@neilwyatt
It’s a mixture of highly aggressive chlorides. There’s no real neutraliser, the best you can do is wash it off immediately with warm water, wash it off again, and then wash it off once more.

For steel, you are better off using a traditional rosin flux or a no-clean plumbers flux for lead free jointing. Steel really doesn’t need a aggressive flux if you clean it first.
27 June 2026 at 13:28 #853708
alecs
Participant
@alecs
Ive always used bicarb soda solution then washed that off with soapy water.
27 June 2026 at 16:20 #853749
Howard Lewis
Participant
@howardlewis46836
Bakers Soldering Flux, as Neil says, is a mixture of acidic chlorides (Mosrly Zinc dissolved in Hydrochloric acid) So needs to washed off IMMEDIATELY after soldering is completed.

Being acidic, an alkaline solution will neatutralise it, but don’t go mad with caustic soda, or you’ll exchange one chemical corrosion problem with another!

Lots of washing and mild alkalis.

Howard
27 June 2026 at 18:27 #853752
Pippin
Participant
@phillspowart84010
Thankyou all. Quite amazed how little it needs, so stuff rusted just from me using the same nitrile gloves I’d used for the soldering.
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