The Shop > Metal Stuff
A Casting Catastrophe
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vtsteam:
David, did you add "Lite salt" or a commercial flux by any chance?

In looking through the Internet I came across the following sentence relative to an aluminum waste dump:

"Secondary processing uses scrap aluminum and/or white dross to create aluminum by adding sodium and potassium chloride salts.  The byproduct of secondary processing is black dross.  White dross contains high aluminum content while black dross contains high levels of chloride, fluoride, and nitrate."
Meldonmech:
Hi Guys,
              Thanks for your comments,
                                                        Mike I do use die castings in my melt together with 50% drawn aluminium, and have found that gives me a good casting that machines well, but your theory could be an explanation.
                        VT, I use table salt as a flux, and sodium carbonate to de gas the melt. There was a heavy crust of around
  25mm on the melt, which would account for the powder coating.
                                                         I am now wondering if any aluminium look alike small bits of scrap with a much lower melting point may have entered the melt, for example pewter.
                                                           The mystery continues.
                                                                                                    Cheers David                                                   
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