Stopping rust on #3 MK1 grenade

[Prometheus]

I have a pretty mint #3 MK1 grenade which has been rusting up pretty nicely for almost 2 years now.
Right now it has achieved a nice brown finish and i would like for it to stay that way and not let it deteriorate any further.
Other than spraying a sealant over it or coating it with some oil, are there any other ways of doing it?
I am not too familar with gun blueing. Does it slow down the rusting on steel?

 

[Serafino]

Bluing would color the metal and probably remove/change some of the existing color.

So long as we're not talking actual red rust, you might try 'museum wax', which is in fact used in museums to protect patinaed metal surfaces from continued corrosion. That's a controlled environment, but it should work in a normal home as well.

 

[rigormortis]

I like the wax idea, but you'll eventually want to seal it. Air + water + iron = iron oxide (rust). Stop the air and water (humidity) from reaching the metal and it'll stop the corrosion.

Neat page detailing how rust starts: http://science.howstuffworks.com/question445.htm

 

[DL 44 Blaster]

I'd seal it......a nice dull coat acrylic wouldn't change it's look.