10 percent w/v citric acid in dionized water, preferably with the addition of 1% w/v thiourea as an inhibitor, but not essential.Twenty degrees C for about 24 hours and it should be gone leaving pinholes and bare metal underneath. Passivate for one hour in 1 molar sodium hydroxide, then water, then 60% alcohol to dewater. Air dry, or oven at 80 degrees.
Never use hydrochloric or sulfuric acid for this reaction.
If you then coat it with a sealant it will then last with the patina of the original. Wax can work if it it is flame applied, but something like the new diamond clear by KBS might be better if you want no maintenance and aren't keeping it to collection standard.
This method works very well where the ongoing preservation of the original part is desired, given how worn original items are trending to far exceed the cost of restored/replica. Can be used with rusty iron in general provide you take chemical safety precautions. It will dissolve the corrosion, and leave the iron and chrome and sub plate through chelating the dissolved ions. Used successfully on cars that cost 1,000 times as much as our beloved swedish iron..