[TheForge] Pickling problem

[Andrew Vida]

What if the flux on the rod was some fluoride?

I tried fluoride fluxes.  I despised them - they did not seem to work 
any better than borax and arguably worse, and left this horrid back-ish 
goo all over the work and which was a bitch to remove.  That is the only 
thing I can think of.

Bruce Freeman wrote:
> Recently I made a test piece - a candle "socket" and
> drip cup for a chandelier.  To keep it "simple", I
> forge-brazed the socket (a piece of pipe) to the cup
> (a saucer-shape) with a copper-based flux-coated
> brazing rod with supplemental borax flux.
> 
> The pipe and, especially, the flat were rusty, and I
> had ground down to base metal only where the braze was
> to be - the rest remaining rusty.  The rust wouldn't
> hurt the final piece after normal cleanup.
> 
> Well, something happened unexpected.  The "rust"
> turned into a thick, black layer, quite unsightly. 
> "No problem", I thought - I'll just pickle it off. 
> Well, a day or more in sodium bisulfate pickle (albeit
> of uncertain strength) hardly touched it.  
> 
> So I tried electrolyzing it off in a bicarbonate bath
> @ 12V (excessive, but my charger does only 12V).  That
> obviously worked somewhat, but slowly.
> 
> Next I tried muriatic acid - straight.  It's been in
> that for a day now.  It's at about freezing, but the
> reaction rate would only be about twice as fast at
> room temperature.  I see small progress.
> 
> So I'm thinking some really strange chemistry must
> have happened in that flux.  Rust + borax + rod flux
> (which is what?) seems to have given a black
> glass-like compound not very amenable to  pickling
> off.
> 
> In retrospect, I'd have cleaned the piece first.  (No
> loss - it IS a test piece.)  I've never had this kind
> of trouble using clean metal.
> 
> Anyone have any similar experiences or know what's
> going on here?
> 
> Bruce
> NJ
> 
> 
> 
> 
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-- 

     -Andy Vida
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Dear head on the wall,
forget what we already know.
Hang a picture of your heart,
bandaged in a surgeon's bowl.

Opened up to it all.

A pity, pretty head.