Sciencemadness Discussion Board

Covering Fluxes

redmoon - 8-12-2010 at 03:09

Hi everyone,

I need a covering flux that has a low melting point such as 200 celcius degree or less. A salt flux may be helpfull. I am looking forward your advices.

Thanks :)

not_important - 8-12-2010 at 09:41

What is it covering? Most low MP salt mixes as based on alkali metal nitrates or hydroxides, both of which are likely to react with many metals.

At the temperature you want I suspect you'll hae to go with organics, even just plain oil.

redmoon - 18-12-2010 at 05:11

i need flux to cover lead metal

Magpie - 18-12-2010 at 08:19

I have done fire assays on gold ore having a quartz matrix. For this assay PbO is reduced to lead which collects as a button at the bottom of the crucible. IIRC my furnace temperature was in the vicinity of 800-900C. I used a salt (NaCl) cover as recommended by Ammen in his book "Recovery and Refining of Precious Metals." Ammen also cites the use of borax as a cover.

melting points:

Pb................327C
NaCl.............800C
Na2B4O7.....741C

Is this relevant to what you are trying to do?

[Edited on 18-12-2010 by Magpie]

watson.fawkes - 18-12-2010 at 08:34

Quote: Originally posted by redmoon  
i need flux to cover lead metal
If it's chemically compatible with what you're doing, you could use refined bitumen, used commercially as roofing tar and for asphalt roadbed repairs.