Removing rust from woodworking machines has been discussed over and over again with each woodworker giving his/her method of accomplishing the same task. They all work to some degree.
Most articles I've read refers to table saw rust and how to clean rust from table saw. Table saws with cast iron surfaces are a major culprit but any machine with a cast iron work surface must be maintained to prevent rust. It doesn't have to be a working surface that has to be maintained either. It can be a drill press column or even hand tools.
Where to start depends on how bad the machine surface is rusted. Most woodworkers have to deal with thin surface rust from a damp garage but some also may be trying to remove years of rust that has pitted the surface. A completely different approach is required for each one.
Basically it's a three step approach. Remove the rust, clean the surface and then seal the surface so it doesn't happen again. Sometimes it's the first step, removing the rust, that has some woodworkers scratching their head.
A LIGHT DUSTING OF SURFACE RUST
On unprotected surfaces rusting starts immediately. Overnight, with the right moisture conditions, a top can rust to the point where it leaves a film on your wood or hands. After a few days the entire surface will be deep dark red color. If this is the level of rust you need to get rid of then it's quite easy following the steps below.
Using a synthetic finishing pad, scrub the surface until all the surface rust is gone. You can do this by hand or you can attach the pad to a random orbit sander. It may be tempting to use sandpaper and try to get all the discoloration out of the surface but you could damage your work surface. Personally I'd rather have a discolored top than a top that's uneven from too much sanding. Sometimes a wire detail brush is handy to get into the corners and grooves.
After scrubbing and cleaning, the surface needs to be wet scrubbed with a rust preventing lubricant such as WD-40 or a light penetrating oil. Cast iron is a very porous metal so scrubbing with a lightweight oil will force the oil into the pores and help seal the surface.
REMOVING HEAVY RUST
Heavy rust that has already caused pitting has done quite a bit of damage and is much harder to get rid of. After it's gone the remaining surface will also be hard to get back as flat as it should be.
One good way is to dissolve the rust is with Naval Jelly. You may have to use several applications before all the rust is removed.
Always follow the directions on the container and make sure to use goggles and rubber gloves. The phosphoric acid that dissolves the rust can be harmful to anything it touches including skin, eyes, and painted surfaces. After using, it can be neutralized using lime or flushing with lots of water.
PROTECTING FROM FUTURE RUST
Now that your machine surface is rust free the next step is to keep it that way. Oil and silicone are both very poor choices.
Over a period of time, if the machine is in a damp area, the moisture will get between the oil and machine surface and start rusting all over again. Silicone is even a worse choice due to the silicones incapatability with most wood stains and finishes. That leaves what I've used for years. Wax!
Several good coats of paste wax will protect your surfaces better than anything else I've found. It also makes your boards slide across the work surface much easier. You can feel when the wax is wearing thin as the boards get harder to push through the machine.
I prefer using a good automotive wax because it seems to last much longer. I've read reports to stay away from automotive paste wax because it may contain silicone. I personally haven't had a problem with it transferring to my wood after it's been wiped down and buffed.
A good paste wax will also protect your cast iron surfaces but seems to wear off much faster. Whichever one you choose should work well. Wax all your tops on a regular basis and you shouldn't have to worry about removing rust again.
REMOVING RUST - Step by Step...