What products (or techniques) have people used releasing rusted on bits where no damage to the part(s) is required?
My Laguna's rear wiper arm is rusted solid and I want to free it off. I've sprayed WD40 on it over a few days (once or so per day) to let it
seep in but that hasn't had any effect.
I recently had to do this on a 206 rear wiper. I tried wd40, a small bearing puller, but neither helped. In the end I used a dremel solid cutting disc on the arm (it was knackered anyway) and cut a slot in the side of the metal bush. Then it dropped off. Lots of white corrosion on the mating faces, so I suggest petroleum jelly or similar when re-fitting.
I was hoping not to have to break the arm as I'm effectively broke.. I can't afford Renault's prices!
Electrolysis? 
I'd agree with balidey, a small bearing puller is probably all that will work.
or 2 prybars with something behind to protect your bootlid?
any jointing compound will help when reassembling, you could even use copperslip as it is a splined fitting.
I made a crude puller with a couple of bits of strip metal and some machine screws - only works if you can see the top of the wiper shaft!
On my Yaris I had to strip out the whole shaft and clean all the rust off it - by its very nature the thing's going to get rained on, sprayed
with salt, etc. So what do they make the shaft out of? Mild steel, of course! 
It's now got copper grease everywhere...
quote:
Originally posted by andyd
I was hoping not to have to break the arm as I'm effectively broke.. I can't afford Renault's prices!
quote:
Originally posted by David Jenkins
On my Yaris I had to strip out the whole shaft and clean all the rust off it - by its very nature the thing's going to get rained on, sprayed with salt, etc. So what do they make the shaft out of? Mild steel, of course!
I pull the whole covers off the wiper area and oil the joints and the spindles, makes a huge difference to the speed and life of the mechanisms. Most
of the ball joints used in them are very poor quality plastic ones that have no lubrication.
Spindles, hinges and locks, the most neglected bits of a car...
Makes it all the more dodgy cos it's the rear screen and on the Laguna it goes through the screen not below on some bodywork. Don't want to
be yanking on it in case the screen cracks!
May have to carve it off after all. 