Steel in a boiler connection?

[baron4406]

Building my first still now, Will probably have 3 or 4 by the time I'm done. Right now I have a pot still the Forum Member Samohon design I saw on here all built, plus a valved Reflux head still. My boiler is the infamous old milk can. I want to make the pot still and reflux still interchangeable on the boiler. The problem has been the boiler connection, I really don't like the connection of the Samohon design i can only get a 1 1/2" hole in the copper cap and still have room for bolts/gasket. So I was rummaging around all my old auto parts and I found a small 4 bolt flange that I could solder a 2" copper union to. Only problem is its mild steel, would this be a problem?