Using electrolysis to remove rust from blued item?

[peregrinvs]

Thanks for all the input. A thought has since occurred...

Am I right in thinking that bluing is a controlled way of adding a layer of black oxide to the surface of the metal? If correct, why will electrolysis not remove this along with the red oxide (rust)?

Having said that, I'm not sure whether the finish on a British made FN-FAL magazine is bluing or a chemical finish like parkerising?