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Old 09-10-2020, 11:34 AM
2152hq 2152hq is offline
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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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