I'm trying to make a 5 pound casting of aluminum with a copper tube (regular old air conditioning type pure copper) to make heat exchangers. The foundry
can only do sand castings.
Problem is the copper dissolves in the aluminum, doesn't melt, so I need to protect it some way from coming in contact with the molten aluminum.
Electroplating won't do, unless it is easy to do. That is, unless it is a rather unsophisticated process where I could order a solution from the local chemical supplier...(but then I've got to get rid of the spent solution...)
If there is some way to coat the copper with a substance that would not impede the heat transfer too much... I have had the idea of using Sodium Silicate (Water Glass) to coat the copper but don't really know how it would work. Someone else suggested using a type of varnish.
Others have suggested mould release products but they have not worked. Almost but not quite. When I cut the casting open to see what happened, I can discern several places where the aluminum came into contact with the copper tube and began to dissolve it, then breach into the tube itself.
If anyone has any insight as to how to do this I'd be very appreciative for some direction... I know it can be done with out too much trouble.