I'm sorry, but Muc-off won't shift electromagnetic plating. Muc-off may tarnish the finish, but you need to use an abrasive with plenty of elbow grease. If you use a coarse grit emery or wet and dry, you will then have hours of rubbing down with progressive finer grades and polishes to restore the shine.
I reckon blast cleaning would work best. Walnut shell being the best abrasive for the task assuming the original finish was highly polished. Sand is way too coarse but bead would give a shotpeened finish.
Or sand by hand and get them powdercoated.
BTW, anyone know a blast cleaning company in the South East region that can do aluminium frames without trashing them?