The 1950 caddy I’m working on sits outside under a tree. It gets rained on and sun baked every day. It has plenty of paint chips, bubbles, exposing rust and same with the chrome. The paint is also so old that theres no clear coat left (if there ever was one?). So in an effort to slow the rust I sprayed some areas with WD-40. Naturally that got on the body here and there, and when I began to wipe it it just made everything glossy. I hit the point of no return and decided to do the whole thing. Bumpers, body and all. Is this bad for it? I assume after some more sun and rain it’ll look streaky, but my main concern is protection at this point. Ultimately the paint has to be sanded off and the body bondo’d and sealed up and repainted.
From the WD-40 website:
“What surfaces or materials are OK to use WD-40 Multi-Use Product on?
WD-40 Multi-Use Product can be used on just about everything. It is safe to use on metal, rubber, wood and plastic. It can also be applied to painted metal surfaces without harming the paint. Polycarbonate and clear polystyrene plastic are among the few surfaces on which to avoid using a petroleum-based product like WD-40 Multi-Use Product.”
You’re going to repaint the car anyway, so it probably can’t hurt. But after sanding down to bare metal you may need to wipe down thoroughly with acetone or the like to remove any WD-40 residue before applying the primer.
cool thanks for that @jesmed1
post wd-40
pre wd-40
Oh yeah, I remember you posted about this Caddy a few months ago. How’s it going?
I don’t know anybody that sands off paint anymore although I suppose there may be some holdouts. Most places media blast it off or a few do chemical stripping. The hazard with sanding has always been driving contaminants into the base metal scratches and pores. Then it’s a real bear to get the metal clean enough for painting. If you have to clean the body to strip off contaminants like wax and oils, you might as well just chemical strip in the first place.
Personally, I don’t believe your efforts will be worthwhile and may just make the task of painting later that much more involved. WD-40 isn’t well suited to the goal in the first place…
Rust is a fairly slow process on mothballed cars. Just look at some of the ancient hulks in traditional junkyards. You can do some things to minimize it- like not parking it on dirt with vegetation growing under and around it. Put down a tarp and top with some stone at a minimum and that will cut down on the moisture quite a bit.
Too late, because the OP said he already wiped the WD-40 all over. I wouldn’t have done it in the first place, but now that it’s done, he may as well leave it there.
You are right that chemical stripping or media blasting would be better than sanding.
I know, I cringed when read that only because I’ve seen the effects of polluted body panels where the extent of the pollution was not known and resulted in a botched job that had to be started over…
Yeah, bad idea, don’t do it again. Only time to maybe use WD-40 is to get road tar off of good paint (but I prefer Turtle Wax tar remover). WD-40 isn’t a rust preventative, it might even make it worse.
I have used WD40 on car paint without any side effects. I use it to remove pine sap.
( also rejuvinates old guitar strings )
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Yes, it’s also good for getting pine sap off of your hands after tree trimming. But I digress. 
WD40 will definitely not make rust worse.
“WD-40 literally stands for Water Displacement, 40th formula. That’s the name straight out of the lab book used by the chemist who developed the product back in 1953. The chemist, Norm Larsen, was attempting to concoct a formula to prevent corrosion—a task which is done by displacing water” straight from the website.
I’ve never painted a car before, but I do paint houses and understand how contaminants can cause paint to not adhere. I didnt know if sanding was the method or whatever - I guess chemical peeling is the proper way, which I’m sure will remove everything. Itll be a long time before painting this car is nearing the top of the to do list.
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@jemsed1 its going well. Needs brakes, tires, and the overheating issue to be solved. But its a project. I still drive it down the block from time to time just to keep it moving.
@Fender1325 - I was remembering old advice about WD40 causing corrosion on guns, turns out to be incorrect. Here’s a comparison of different sprays, WD40 was OK, not the best:
But I wouldn’t use it all over the car, mostly because you’ll want to do some painting at some point.
Although It got bad ratings in that gun article, I’ve heard good things about Kroil in terms of busting off rusted nuts
That article was just for rust prevention, not breaking frozen nuts free.
What do you need paint for @Fender; She looks good now.
Just set up a mister that the car passes under on the way back inyo the garage.
Yosemite
WD-40 gums up after a short amount of time. Keep it away from hinges, etc. It gums up and attracts dirt and under a tree you will have puddles of gooey cra*. Be careful.
How about buying a tarp?