I'm not really sure what you would want to do with chrome, aside from polishing with 00 steel wool, or aluminum foil. This would not help much if it is extremely rusty, but might be a good way to see how bad it is - sometimes the rust "blooms" and appears thicker than it truly is.
If you can remove the rust to the point it looks presentable, perhaps coat it with a museum or coin wax (such as used by numismatists) to protect it - thought it will likely wear off with use.
Perhaps boards related to gun-metal may offer you some different ideas.
On the chance you may expect to refinish the column (paint it), you might venture into some automotive boards. Of course, your enlarger will not be exposed to the elements, but there is some information that might be useful to you.
Specifically, I'm talking about "rust converters;" typically, you don't actually remove all the rust when using these, aside from a wire brush to remove the scale. SEM Rust-Mort is one example, but there are other companies with similar products:
http://www.semproducts.com/rust-and-corrosion-rust-converters-sealers/rust-morttm
They are expensive, though, and may be overkill for your application. It is also more involved than simply using a can of rustoleum. If you go this route, use thick rubber gloves - I know for a fact it will seep through vinyl
) to prevent rust. 
