You might try galvanic corrosion. I am going to try and describe this from memory. You should probably Google it. It worked real well in cleaning up some of the old bronze from my BB15, ELF.
1. I used a casserole dish. Line it with aluminum foil.
2. Fill the dish with boiling water.
3. Super-saturate the hot water with salt and baking soda.
4. Soak the items you wish to clean for about, hmmm, 2 hours?
5. Remove cleaned items.
Essentially, the aluminum has low galvanic nobility and acts as a "martyr". At the end of this exercise, you will be surprised by how much the aluminum foil has deteriorated. The bronze has much higher nobility and, consequently, is safe. Chrome is somewhere in-between. I don't know if it will work, but you could give it a shot.
