Ladle Wash...
...and Alumina refining
It
took some looking, but eventually "the wife" was able to find the
heart of this project.
After having had lost so many melting pots to either Magnesium or just deterioration due to use, the idea of applying some sort of coating to extend the life of the pot was worth investigating.
The gray material behind the box of Borax is about 200-300lbs of blue clay I dug out last summer with the tractor after we had a pond dug.
Whether this is Kaolin clay or bentonite clay is irrelevant, as it is clay, and is the only clay that I have a reasonable quantity of.
Again the Electric Wheel chair mixer is put to use... The dark powdery substance is the powderized dross from aluminum melts.
The dross is actually Aluminum oxide or alumina... Alumina is a rather robust chemical in that it's closer to a ceramic than a metal and can withstand a considerable amount of heat.
The material all started out quite coarse but after 2 1/2 hrs of tumbling reduced to a nice even consistency.
This is approx 1kg of the refined Alumina.
I have 4 large buckets that need to be mechanically refined and re-melted to recover what metal is left and get as pure a composition as possible.
By chance I wiped the corner of my mouth with the back of my hand, and could taste the saltiness of the dust from the alumina.
The flux agent that aids in separating the dross from the melt is a sodium based chemical (I think it's just a salt).
So I've opted to wash the alumina with hot water and filter off the saline liquid.
The qty of Alumina was washed 4 (four) times before I could no longer taste any salt... It has been 2 days and I'm still alive and feel no ill effects...
Though I wasn't stuffing mouthfuls of the mixture in my gob either...
The washed Alumina is sun dried so that the weight measurements between the other dried components is consistent.
This is a dandy "German" digital scale that I procured from Canadian Tire for about $50.00.
I don't use it everyday, but on occasions like this it's nice to not have to guess.
The scale is "Zero'd" with the container and ready for action.
50 grams of Alumina, washed and dried...
50 grams borax
200 grams of blue clay
The above ingredients are mixed with water to the consistency of a milk-shake.
The pot on the far left is near it's end and would likely be good for only 2 or 3 more melts before I would decommission it, the other 2 (two) have yet to see any action.
Obviously I'll have to double or triple the qty of the ingredients as I ran short.
The insides were more liberally coated than the outsides.
The pre used pot stood-up remarkably well as I put 3 full melts through with the inside lining still completely intact. The exterior began to flake-off immediately once the burner was engaged, but didn't get any worse once warmed up...
The popping sounds that accompanied the flaking were likely moisture that was under the scale of the used pot.
The skin of aluminum once cooled peels out like aluminum foil.
This pot will be re-coated as many times as possible to see how long the coating can extend it's life... but it looks pretty good so far.
This is a 6" by 8" scrap pot, in that it is used for refining scrap into ingots.
After close to 6 hrs continuous burn-time it produced close to 90 ingots and looks near perfect.
The refining process seems harder on the pots as the scrap is dirty and the fluxing salt tends to accelerate the decomposition of the metal walls.
On both pots the inner lining is a very hard surface and stood-up to considerable scraping as the metals were added.
The lining can be picked off, but does seem to have adhered to the surface better than I thought possible given that I thought it would have been more fragile.
So in closing for the foreseeable future I will coat my melting pots with this mixture prior to foundry days to reduce contamination of the melt, and extend the life of the pots themselves.
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