One useful solution is Dave Gingery's method of using crucibles made from
"iron" pipe: he coated the inside with a thin wash of refractory clay
and
allowed it to dry before using the crucible to melt aluminum.
Ed Huntress



This will work if you have to use a steel pipe crucible and is a good
plan even with a cast iron pot. I discovered the solvent properties
of molten aluminum back when I first started casting and decided to
make a crucible from a length of 4" i.d. steel pipe with a 1/4" thick
plate welded to the bottom. I fired it 4 times and a hole formed in
the bottom. It was just a pinhole but it was enough to let aluminum
flood the bottom of the furnace. Now I melt aluminum in a cast iron
pot coated inside and outside with furnace cement from the hardware
store thinned with water to a thick paint and brushed onto the warm
metal. This lasts for 2 or 3 heats and can easily be renewed when
neccessary.

Mike