How To Clean A Rusty Electric Motor

Melvin Munly1949 · Wednesday, December 8, 2021

Can one use WD40 to clean idler motor

I'm in the process of cleaning up my very dirty idler motor. I've taken it apart and blown everything out as well as wire brushed the rust off the thick magneto parts(don't know what these are called but all the wire windings run through them and they are the big drum looking things with one fitting inside the other and it rotates).
Is it ok to spray a light film of wd40 in there to prevent rust in the future? I've read where some have done this but my experience with wd40 is that it leaves a diaelectric film that hurts conductivity. I do have electric motor cleaner that I can go back and spray the motor with to clean these parts off if anyone believes it a better bet to remove the wd40 light film that I've applied.

thanks in advance for help.

E

Last edited by imported_eric_h; 07-26-2009 at 09:47 AM.
Originally Posted by imported_eric_h

I'm in the process of cleaning up my very dirty idler motor. I've taken it apart and blown everything out as well as wire brushed the rust off the thick magneto parts(don't know what these are called but all the wire windings run through them and they are the big drum looking things with one fitting inside the other and it rotates).

Stator and rotor.

Is it ok to spray a light film of wd40 in there to prevent rust in the future? I've read where some have done this but my experience with wd40 is that it leaves a diaelectric film that hurts conductivity. I do have electric motor cleaner that I can go back and spray the motor with to clean these parts off if anyone believes it a better bet to remove the wd40 light film that I've applied.

Leaving the WD40 will just attract dirt. Get a product that removes rust and
protects the surface from future rust. I have used "The Must for Rust". There
are similar products available.

E

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I would reccomend the electric motor cleaner, then go back and put a product like Rons suggested on the parts that would suseptable to rust. That way no rust or residue. In my understanding electric motor cleaner is like brake cleaner in that no residual film is left. I use a product from NAPA (part# 4700) that states it can be used on both electric motors and brakes, as I said you would have to go back with somthing else to apply to rust prone parts after cleaning.
Hope this helps, Doug

Last edited by doug8cat; 07-26-2009 at 11:36 AM. Reason: spelling
When I cleaned out the motor on my big lathe, one of the guys at the museum, who was a retired power company engineer, reccomended using mineral spirits, as that's what they used on their generators. I had a spray can that hooked to an air line (you can get these at HF), which essentially made a mineral spirits pressure washer. I blasted the windings spotless. Let it dry in the hot sun for an afternoon and then let it dry in the shop for another couple of days. No problems in four years now.
Beware any brake cleaner product, other than the one above that is labelled for use on elecric devices. Most brake cleaners have mean solvents in them that will eat the glyptol and varnish wire insulation.
Excellent info. and I will get some of the product that was recommended. If I can't find it then I'll go with the mineral spirits.
Thank-you all for your comments,

E
Originally Posted by Mike C.

Beware any brake cleaner product, other than the one above that is labelled for use on elecric devices. Most brake cleaners have mean solvents in them that will eat the glyptol and varnish wire insulation.

Mike,
I can't speak for glyptol but I have never seen anything short of a rat tail file that will touch varnished magnet wire, certainly not brake cleaner or solvent.

Stuart
the rust is on the stator and rotor...sorry I didn't know the part names. I have wire brushed these well but just want to have something that will protect them from rust after I put about 4 hours of elbow grease into cleaning them up.
E
WD40 is basically stoddard solvent which is close to mineral spirits. But if you want
to protect the steel laminations from rust, you could just mask things off and shoot
a quick, thin coat of primer on the laminations.
I did this on my truck alternator, when I discovered that the stator had rusted
to the point that the rotor was locked from turning!!

After, of course, using a small drum sander to clean off the inside of the stator.

Jim
Originally Posted by jim rozen

But if you want to protect the steel laminations from rust, you could just mask things off and shoot a quick, thin coat of primer on the laminations.

Jim

Primer will eventually flake off. Get this product or similar:
Cling Surface - Heavy Duty Rust Inhibitor Coating
ITW Fluid Products Group
10.75 oz. spray can
$13

Gives long term metal protection
Will not flake
Indoors or outdoors
Contains no Fluorocarbons

A homemade solution:
Buy a brick of beeswax and pour a pint of turpentine into a jar.
Shave off flakes of the beeswax into the jar and stir.
The flakes will dissolve. I like the consistency of peanut butter.
Then brush it onto your metal.
You won't see any rust.
would this beeswax concoction prevent the stator and rotor from having good conductivity between the two?
thanks,
e
Eric,
There is an air gap between stator and rotor, they don't touch. The beeswax won't affect the magnetic field...nothing will.

Stuart
Remarkable new material to keep steel from rusting. Called "paint."
Don't like primer? Grab a rattle can that is not primer then.

Jim
I thought of another method. I recently re-wound a power transformer for a
battery charger I am making. I used clear finger nail polish to coat the
windings and core laminations. I checked out a couple of 3M coatings but
one was red and the other was black. I couldn't get clear so I used the clear
lacquer nail polish. Check the 3M website if you are interested. That material
is what they use in stator windings. Nail polish is a second choice. A clear coat
from a spray can is a third choice but I admit that it is the easiest.