borax-containing starch as flux

Thread Starter

bootlegengineer

Joined Dec 5, 2016
57
I know this isn't exactly an electronics question, but it does pertain to soldering, so I thought I'd give asking this question a shot.

So I found this bottle of sta-flow concentrated liquid starch and read the ingredients on the back. I was interested to find that it contained borax among other things that don't really pertain to flux as far as I know (corn starch, processing aids, preservative, ironing aid, and perfume). My question is can I possibly use this as a fluxing agent for brazing and/or soldering? And if not as a standalone product, how about if I were to add zinc chloride and some hydrochloric acid?

Edit 1: From what I read the ironing aid is made from some kind of lubricant such as sulfonated castor oil.

Edit 2: I apologize. I should have been more specific with what I was planning to solder/braze. I'm trying to join two copper pipes together. I figured that pure borax wouldn't work for soldering, but I do remember people talking about using borax and water as a makeshift flux for brazing, which is why I was asking.
 

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jpanhalt

Joined Jan 18, 2008
11,088
At brazing temperatures, the cornstarch and other stuff should decompose/char which might add contamination, particularly if the metal is a little hard to wet (SS?). I would use flux designed for the purpose.
 

shortbus

Joined Sep 30, 2009
8,728
How or why would you think it would work? You do understand the purpose of flux in doing the brazing don't you? And for soldering even straight pure borax won't work, because of the temperature involved.
 

jpanhalt

Joined Jan 18, 2008
11,088
I thought for sure you were talking about brazing. Now, I see the soldering part. Like @shortbus said, borax will probably not work at ordinary soldering temperature. As for zinc chloride, that is usually found in flux used for plumbing. It is acidic will cause corrosion in electronics.
 

shortbus

Joined Sep 30, 2009
8,728
They do use some starch in the flux of stick welding rods though. Has nothing to do with the welding part though, it just makes the flux stick to the rod until it is dried in the oven during processing.
 

Thread Starter

bootlegengineer

Joined Dec 5, 2016
57
They do use some starch in the flux of stick welding rods though. Has nothing to do with the welding part though, it just makes the flux stick to the rod until it is dried in the oven during processing.
Oh wow I had no idea that was how they made flux stick to the rods! I gotta remember this when I eventually make my own SMAW electrodes!
 

shortbus

Joined Sep 30, 2009
8,728
Oh wow I had no idea that was how they made flux stick to the rods! I gotta remember this when I eventually make my own SMAW electrodes!
Why? It, the starch only keeps the flux from falling off until it shrinks down from the heating. Where would you even get the *recipe* for the flux? Every type of rod has a different flux content. and you would also need some sort of extrusion machine that the wire goes through while getting the flux on evenly around it.
 

Wolframore

Joined Jan 21, 2019
2,321
I remember hearing from a customer that they figured out how to save a ton of gas by mig welding with some sort of cleaning liquid, it wasn't soap. But spraying this on stainless they were able to get clean welds without flux or shielding gas. I wish I remembered what the product was.
 

Thread Starter

bootlegengineer

Joined Dec 5, 2016
57
Why? It, the starch only keeps the flux from falling off until it shrinks down from the heating. Where would you even get the *recipe* for the flux? Every type of rod has a different flux content. and you would also need some sort of extrusion machine that the wire goes through while getting the flux on evenly around it.
I'm not looking to make professional welding rods for serious work. I simply just want to have in my mind a method of making stick electrodes in the event of an emergency. Limestone and carbon are both used together a lot to smelt down iron ore because it creates a protective slag layer above the molten metal pool and also remove oxygen from the ore, creating pig iron. If I combine limestone and carbon, I can make a very basic calcium oxide based flux. You can also add varying amounts of feldspar, silicates, silicon dioxide, iron powder, and manganese powder if you want to get fancy and have any of those ingredients.

Also in terms of getting an even coating, all that is really needed is a small pipe, and then a way to keep the uncoated rod centered, such as two pipe caps with holes drilled in the centers.

Also, here's an msds for a 7018 rod, which includes the ingredients its made of: https://amp.generalair.com/MsdsDocs/ESAB7018S.pdf
Its not hard to find this info. Just search "_______ electrode msds".

I remember hearing from a customer that they figured out how to save a ton of gas by mig welding with some sort of cleaning liquid, it wasn't soap. But spraying this on stainless they were able to get clean welds without flux or shielding gas. I wish I remembered what the product was.
This has me very interested. I'll get right to researching and experimentation!
 
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Thread Starter

bootlegengineer

Joined Dec 5, 2016
57
I remember hearing from a customer that they figured out how to save a ton of gas by mig welding with some sort of cleaning liquid, it wasn't soap. But spraying this on stainless they were able to get clean welds without flux or shielding gas. I wish I remembered what the product was.
not sure if this is exactly what you're looking for, but this seems to fit the description you provided:
https://superiorflux.com/tube-welding-flux/
 

Wolframore

Joined Jan 21, 2019
2,321
Maybe they bottled it and branded it to sell for multiples of cost. From what I recall it was an inexpensive cleaner which I'm sure they discovered by accident. I just never got the brand and which one it was. I should call my old engineer to see if he remembers.
 

shortbus

Joined Sep 30, 2009
8,728
I have used borax in a pinch for silver soldering.
Max.
But the silver solder is done at a much higher temp, just slightly under brazing temp. I took when he mentioned soldering that he meant soft soldering. It takes ~1370°F for borax to go liquid, then slightly more, depending on the grade of silver solder, for it to flow.
 

Thread Starter

bootlegengineer

Joined Dec 5, 2016
57
But the silver solder is done at a much higher temp, just slightly under brazing temp. I took when he mentioned soldering that he meant soft soldering. It takes ~1370°F for borax to go liquid, then slightly more, depending on the grade of silver solder, for it to flow.
Yea again I apologize for not being specific in my original post. I had a lot going on when I posted (making components for a furnace and repairing compressor piping), so I didn't think through what I was going to say very well when I should have.

Maybe they bottled it and branded it to sell for multiples of cost. From what I recall it was an inexpensive cleaner which I'm sure they discovered by accident. I just never got the brand and which one it was. I should call my old engineer to see if he remembers.
Aight cool! Sounds like this stuff could be a real game changer for those who are on a really tight budget and need to save every penny they can! I'm sure there's a lot of that happening now a days what with covid decreasing the number of jobs and all that. Kinda sucks that this whole epidemic happened just a couple months before I got my welding certs. Now there aint no jobs! :p
 

shortbus

Joined Sep 30, 2009
8,728
Kinda sucks that this whole epidemic happened just a couple months before I got my welding certs. Now there aint no jobs!
don't know where you live, but there are around here. My one grandson who is a senior in high school just started a job working 1/2 a day as a welder. That's what he was taking in school.
 
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