Can Aluminum Shield Magnetic Fields?

Yes, this can still work as a transformer. However, many unspecified and unmeasured parameters will determine how much less efficiently will this new transformer work. The magnetic permeability of Aluminum is about 5000 times less than iron but the closed conductive loops of an aluminum tube (and the iron rod) will convert some of the electrical energy into heat.

If you wind the secondary over the primary, then it should work. This should also work if the core is a wood dowel.

A straight rod is sort of the ultimate transformer air gap, I guess.

Now I understand. The wood dowel make things clear.

Thanks. I have not thought of the aluminum tube as an extra short-circuited turn of conductor wasting power.

The iron core is a questionable choice, use a ferrite rod from an old radio for better result.

As other have said, the open magnetic loop (long airgap) will require an enormous amount of turns to increase the primary magnetizing inductance.

As for you aluminium protection tubing, if you must use it instead of plastic, cut a slit along its length to open up the circuit and avoid shorting your transformer.

Thanks for the hints. My original post was just to ask about introducing the aluminum tube. Indeed it would short - may destroy - the primary windings as the single turn has very low resistance/impedance.

I doubt the value of the ferrite from an old radio will be of much value at 50Hz. If you have ever tried to make a balun the results with different ferrite rings is quite noticeable due to their permeability.

See-Thru Science: Eddy Currents (youtube.com)

Aluminum can partially block magnetic fields, but it is not as effective as materials like iron or steel. While aluminum itself is not magnetic, it does conduct electricity, which allows it to interact with magnetic fields to some extent.

Aluminium is not a very good magnetic shield.

For your project you would be better off using and old E core out of a donor transformer from a plugpack, they are designed to work at mains frequency 50/60Hz. If magnetic shielding is required then put it into a steel box.

Why not use a toroidal transformer, it's self shielding.