I'm a fan of using electrolysis for rust removal, followed by a  
light Scotch Brite pad, brass brush, or tooth brush clean up. It won't  
deal with heavy rust, and it leaves a dark patina wherever it removes  
surface rust. It won't damage plating or japanning that's sitting on  
clean iron, but if there's rust underneath the plating/finish it will  
cause it to flake. The one hassle with electrolysis on #45/#55 planes  
is that you can't easily remove the wooden handles, so you have to  
submerse the metal and leave the wood out of the solution.

   There are a number of articles and instructables on this process,  
but since I don't have any experience with the ones I'm finding I  
opted not to link them. Search fro 2 or 3... the process is simple.  
The details I'd recommend are:

   Pay careful attention to the power supply polarity- negative goes  
to your rusty tool

   Use washing soda or it's equivalent to make the electrolyte. Not  
baking soda, not salt (which I've seen recommended)

   Use a stainless steel plate or bolt as your anode. You can use most  
iron/steel, and the first article I read suggested iron rebar. Ferrous  
metals break down and make a nasty mess whereas with stainless I only  
end up with rust particles in my electrolyte.

   I bought a stainless sheet from the local hardware chain, and I  
wrap that with plastic screening. It provides a lot of surface area  
and the screen reduces the risk of shorting the tool to the anode.

   Good luck,

   Paul

   >> I recently traded one of my gold fillings for an old Stanley 45  
that has about 85% of the nickel plating intact. By the looks of it  
it's spent the last few decades on the shelf  collecting  dust and  
rust.  My question is, do any of you gentelman know of a way to clean  
up the rust spots without removing or damaging too much of the  
remaining nickel finish?  Not expecting a miracle -- I went it over it  
with some steel wool and WD-40 but that's about it.