On Fri, 28 May 2010 11:04:31 -0400, Ned Simmons wrote:
On Fri, 28 May 2010 07:25:11 -0700, "Roger Shoaf" wrote:
"Ned Simmons" wrote
On Thu, 27 May 2010 22:17:36 -0700, Tim Wescott wrote:
....
After finishing soldering my Very First model airplane fuel tank, I
went to do the last step of any soldering project -- cleaning off the
flux.
....
Jeweler's pickle?
http://www.ganoksin.com/borisat/nena...ling-notes.htm
....
Won't the acid be a problem? While not stated, I had assumed that the
fuel tank was made of copper or brass. If you look at the last part of
the cited article it indicated that the acid pickle eats copper.

That paragraph is talking about the pickle plus peroxide. I've never
used that mix so I don't know how agressive it is, but copper or brass
can stay in the regular mix for hours with no apparent damage. This is
effective on brazing flux and I assume would work on soft solder flux,
though I've never tried it myself.

The question about copper or brass probably is moot because in later
posts, Tim said the tank is made of tin-plate steel sheet. (From a
"Dole chunk pineapple can" he said, but it seems to me other brands
or cuts of pineapple might work too.)

Anyway, HCl + H2O2 (which might be but probably isn't what the
ganoksin link refers to) is so aggressive that it's commonly used to
etch copper printed circuit boards. As noted in many web pages, eg
http://www.chemicalforums.com/index.php?topic=40738.0 , by itself
HCl doesn't attack copper, but CuO + 2HCl -- CuCl2 + H2O. Ie, when
copper is immersed in the mix, H2O2 keeps oxidizing Cu to CuO and HCl
keeps on forming copper chloride.

--
jiw