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What's the best flux fluid I can use for stainless steel wire and where can I find it ??

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Hi folks,

I'm after some flux to solder some stainless steel braided wire. The wires are coming from my Lithium Polymer batteries and need to be soldered to gold plated connectors.

I've been told to get "Flux No.71". But I can only find that in big bottles, when all I need is around 25 ml.

Does anyone know where I can get a small amount, (Bar China) or does anyone have any I could buy?

Failing all the above does anyone know of another flux that would work?? (I've tried cheapo flux, Fry fluxite, and LA.CO flux) 

I've used plenty of heat and a large solder tip for quick heat transfer, but I'm still struggling to get a consistent finish.... 😖


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For soft solder try Harris's "Stayclean".   https://www.cupalloys.co.uk/store/Stay-Clean-Flux-125ml-p276411655

I've read that Jenolite de-rust treatment works as it contains phosphoric acid - not used myself.  The traditional way is zinc dissolved in hydrochloric acid until no more will dissolve  - this is quite aggressive and don't breath the fumes during soldering.

I suggest plumbers solder rather than electronics multicore type solders.

Extremely clean and dry first.

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Cheers PopsBengo,

I'll do some research.

I'll give the hydrochloric acid a miss. Although "Flux No. 71" apparently contain hydrochloric acid, along with other acids.... 


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51 minutes ago, Richiew said:


Have you tried this on stainless steel?  Our sheetmetal workers used it for galv. and mild steel but it wasn't reliable for stainless.

This is also recommended  and not expensive https://soldersandfluxes.co.uk/p584/A8-Flux-for-Stainless-Steel.html

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Never seen stainless braid , sure it’s not silver plated copper?? . We use fluxrite for every solder job here at an ex ICI plant but can sometimes struggle to get enough heat into the wires when using welding cables . Might have to use crimps on the braid then solder the copper to the gold bits . Solder with 5 core flux built in works well think it used to be called ERSIN 

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I ended up buying this. I just hope it works.......

P 20 Soft Soldering Flux Paste 140g pot _ solder flux _ eBay.html

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1 hour ago, chaz said:

Hope it works for you.  If you know this please forgive me:  Scuff up the stainless to brighten the surface.  Don't forget any dampness, dirt or grease including finger grease will disrupt wetting-out of the solder.  Try tinning the two surfaces (especially the stainless) first.

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  • 2 months later...

Thanks all now sorted.

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