How are you going to combine? Are ya going to melt them together in a big pot, screw em together, pop rivet them, use some glue or weld them. Is this going to be inside or outside? Give us something.

Anyhow the answer will be all depends, but usually you will not have any galvanic corrosion or electrolysis unless you have water or electricity in them moving around the molecules.

www Metalrecipes -- heat and beat to the desired shape, repeat as necessary.
warren