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Old 09-10-2020, 08:22 AM
Patrick L Patrick L is online now
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How to neutralize Comet flux to keep from rusting? How to neutralize Comet flux to keep from rusting? How to neutralize Comet flux to keep from rusting? How to neutralize Comet flux to keep from rusting?  
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Default How to neutralize Comet flux to keep from rusting?

I have used Brownell's Hi Force 44 solder for years, always with excellent results. I do use the recommended Comet flux.

It seems that the soldered parts seem to have an affinity for rusting though. It seem anywhere that the Comet flux may have run or seeped to starts to rust. If the soldered area is in plain view it's generally not a problem as you see it and wipe it. If the area is hidden, it seems to get away from me and after a week or so there's quite a bit of rusting (at least more than I want, which is NONE.)

WD40, G96, Break Free, etc. will all clean and remove the rust, but it will come back. Is there something that will neutralize whatever is in the metal and keep it from rusting in the first place? I know the old trick of soaking rusty things in vinegar, would that do it?
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Old 09-10-2020, 09:00 AM
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chief38 chief38 is offline
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How to neutralize Comet flux to keep from rusting?  
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After a thorough cleaning, apply a light film of Rig Universal Grease. Rig Universal is the best there is IMHO and that should work. The key here is to remove ALL of the rust prior to application!

HINT: When using ANY Flux (even for electronics or plumbing solder joints) remove as much Flux as possible as it will cause corrosion down the line.


RIG Universal Grease, 1.5oz. : BIRCHWOOD CASEY RIG(R) UNIVERSAL GUN GREASE | Brownells

Last edited by chief38; 09-10-2020 at 09:03 AM.
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Old 09-10-2020, 11:34 AM
2152hq 2152hq is offline
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How to neutralize Comet flux to keep from rusting?  
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Comet Flux is a so-called "acid flux'.

The term is not really a true meaning of what they are, but rather of how they are made.
These types of soldering fluxes are generally a metalic chloride compound.

They are made by dissolving a heavy metal in an acid.

The most common of them is Zinc Chloride.
Zinc dissolved in Hydrochloric acid.

The Zinc Chloride liquid is acidic in PH range,, but not in itself considered an 'acid'.

That the stuff works wonderfully as a soldering flux is unchallenged.
It will even do a bit of cleaning of the surfaces for you should you not clean them properly before the work.
But,,the chemical when heated during the soldering process runs over the work and also creates a gas that is very corrosive.

So you get great solder flux action,,,but horrible after rust when the job is done.

When used to solder steel parts, the soldered assembly should be boiled in water w/an alkali in solution to neutralize the acidic PH.

This and scrubbing the areas to remove and neutralize the flux is needed.

Simple wipe downs, flushing with water (hot or otherwise) just won't do it.
The stuff will still be there and after rust will appear.

Oil or grease will NOT remove the flux or prevent rust if the flux from it's use after soldering is still on the surface.

If you use a lot of it in large soldering jobs in a shop, you'll notice surrounding tools, machines and fixtures starting to rust. That's from the acrid smoke from the flux during soldering use landing on those surfaces. Then they rust.

Acid Flux is a Big No for use in soldering SxS bbls and ribs back together just because of the after rusting problem.
The area inside the rib and bbl void just can't be flushed out and cleaned properly. The use of acid flux will just about guarantee afterrust in there and it will be heavy and damaging.

Some will use it to 'Tin' the separate parts before assembly. Then carefully clear them before sweating them all back together.
The use of rosin flux or other non-rusting flux in the assembly so no after rust concerns inside there.
But,,you still can't be sure you've cleared the acid flux before reassembly IMO.

I just won't use the stuff.
Plain paste flux works fine as long as you clean the metal surfaces well and don't burn the flux with too much heat.

Last edited by 2152hq; 09-10-2020 at 11:37 AM.
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Old 09-10-2020, 11:39 AM
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How to neutralize Comet flux to keep from rusting? How to neutralize Comet flux to keep from rusting? How to neutralize Comet flux to keep from rusting? How to neutralize Comet flux to keep from rusting? How to neutralize Comet flux to keep from rusting?  
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Boil the finished work in a baking soda and water solution to neutralize the flux/acid.
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Old 09-10-2020, 01:53 PM
Patrick L Patrick L is online now
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How to neutralize Comet flux to keep from rusting? How to neutralize Comet flux to keep from rusting? How to neutralize Comet flux to keep from rusting? How to neutralize Comet flux to keep from rusting?  
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Got it! Thanks!

It was a small part, so it will be easy to boil.
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