[LadyMe]

I'm going to second that PB Blaster recommendation. It's the best product for rusted/corroded bolts that I've used.

The first time I used it... I had this rusted bolt I couldn't get off. I tried a variety of things for over a week. It was in the worse place (couldn't even cut it off). I was on the verge of attempting to drill it out when I sprayed it down with PB Blaster - that thing was off 5 minutes later. There's my PB Blaster commercial.

I have used CLR in my heater coil to help clean out the dirt & grime... it works pretty good for that (but I agree with MagicRat - I think if you use CLR you will need to immerse what you want to clean). I also have Liquid Wrench - but I don't think it works anywhere near as well as PB Blaster because I had tried it on that afore mentioned rusty bolt and it made zero impact.