WeldingWeb - Welding Community for pros and enthusiasts banner

Best way to remove WD40 from rusted metal before paint priming

22K views 33 replies 14 participants last post by  sleeper  
#1 ·
So I made a bracket out of some rusted metal and was cleaning some of the heavy rust off with a steel brush. I didn't realize that the brush had WD40 on it from a previous project. I wasn't planning on sanding the thing down and was going to use Rust-Oleum Rust Reformer before painting. Now I got to get the oil off and a Google search said not to use soapy water. I was wondering what you all use to remove oil?
 
#2 ·
You could burn it off.... but the heat may affect other things ;) Personally I love to use chemicals!!!! brake cleaner, carb cleaner, ether, acetone, MEK, etc... lots of stuff to 'cut' oil :D I suppose even dawn dishwashing liquid works good to cut oil... or even simple green plus a whole lot more things sold as 'degreasing' solutions at most hardware stores...
 
#6 ·
Any time we ran out of the commercial wax/tar remover when I was painting, enamel reducer was my favorite go-to. There really isn't a lot of oil in WD-40, it tends to evaporate quite dry, so any old paint thinner or acetone should work. You don't need anything fancy, soak it on with one rag and wipe it dry with a clean rag so you don't leave residues behind.
 
#20 ·
Any time we ran out of the commercial wax/tar remover when I was painting, enamel reducer was my favorite go-to. There really isn't a lot of oil in WD-40, it tends to evaporate quite dry, so any old paint thinner or acetone should work. You don't need anything fancy, soak it on with one rag and wipe it dry with a clean rag so you don't leave residues behind.
Look up the msds, it's 80-90 % kerosene
 
#8 ·
The light layer of rust has soaked up the WD40 so that it looks wet which surprises me how much was on the steel brush. That think that worries me is the Rust-Oleum Rust Reformer and if any of the usual stuff I've used would keep it from working. Thus is the first time I've used Rust Reformer and actually bought it by mistake.
 
#11 ·
If you're leaving enough rust behind after the wire brushing to soak anything up, that's a bigger adhesion issue than the WD-40. If you don't have access to a sandblaster, maybe some light grinding discs or heavy sanding discs. I was working on a piece this afternoon and using 80 grit sandpaper in my RO sander.
 
#16 ·
If you're leaving enough rust behind after the wire brushing to soak anything up, that's a bigger adhesion issue than the WD-40. .
Well that's the whole purpose of the Rust Reformer to paint over the rust. You just can't have flaky rust. I didn't want to take it down to clean metal and don't really care what it looks like, just don't want it to rust anymore.
 
#13 ·
If the remaining rust is absorbent, and if the WD40 soaked into it, I would use a strong base such as lye/sodium hydroxide/oven cleaner with a little dish detergent like Dawn as a wetting agent, and scrub with a brush, then hose off real well, then let it dry. "Rust Reformer" is basically an acid, and if there's any grease at all left in the rust, it ain't gonna be "reformed" because the "reformer" ain't gonna touch it because oil is hydrophobic (kinda like vinegar and oil).

Personally, I would skip the "rust reformer" and go straight from degreasing to Rust Oleum Rusty Metal Primer (a little rust actually helps it adhere by giving it some tooth) but that's just me...
 
#18 ·
From what I've read , WD-40 is a mixture of light mineral oil(less than 10w) and fish oil. Rustoluem red primer for rusty metal (commercial grade enamel, oil-base) also has oil, and fish oil in it. I've painted lots of rusty stuff with the red primer, and never top coated, and it takes about 10 years to rust. I've cut, drilled, and tapped using WD-40 as lube, Never seemed to affect the paint sticking, If it does start to rust, its hard to notice on the deep red finish. I would just paint it after a quick wipe with mineral spirits or acetone, which ever is handy.The reason you don't want to use anything water based is because the rust will soak it up. If you dont get all the water out before you paint,(which would probably take some heat to chase the water completely out) it will probably continue to rust more underneath the paint, cause blistering, and eventually flaking off.
I've used different brands of rust reformer. Some are solvent based, some are water based, and then it has to match you paint. I stick mostly with Rustoleum, and some Benjamin Moore. I would have to check but i think the rustoleum is .......

If you are using the flat black autmotive version I wouldn't worry to much , the SDS I saw has lots of solvents in it.

https://www.rustoleum.com/MSDS/ENGLISH/248658.pdf


3. Composition / Information on Ingredients
HAZARDOUS SUBSTANCES
Chemical Name CAS-No. Wt.% Range GHS Symbols GHS Statements


Acetone 67-64-1 25-50 GHS02-GHS07 H225-319-332-336

Propane 74-98-6 10-25 GHS04 H280

n-Butyl Acetate 123-86-4 10-25 GHS02-GHS07 H226-336

n-Butane 106-97-8 2.5-10 GHS04 H280

Hydrous Magnesium Silicate 14807-96-6 2.5-10 Not Available Not Available

Xylenes (o-, m-, p- Isomers) 1330-20-7 2.5-10 GHS02-GHS07 H226-315-319-332

Dimethyl Carbonate 616-38-6 2.5-10 GHS02 H225

Hydrotreated Light Distillate 64742-47-8 1.0-2.5 GHS08 H304

Ethylbenzene 100-41-4 0.1-1.0 GHS02-GHS07-

GHS08 H225-304-332-351-373

Carbon Black 1333-86-4 0.1-1.0 Not Available Not Available

Naphtha (Petroleum), Heavy Aromatic 64742-94-5 0.1-1.0 GHS07-GHS08 H304-312-332

Zinc Phosphate 7779-90-0 0.1-1.0 Not Available Not Available

Sulfonic Acids, petroleum, calcium salts, overbased 68783-96-0 0.1-1.0 GHS06 H331

Zinc Oxide 1314-13-2 0.1-1.0 Not Available Not Available

Methyl Ethyl Ketoxime 96-29-7 0.1-1.0 GHS05-GHS06 H302-312-317-318-331


HTH

Good luck
 
#27 ·
Oh man!!! I don't know... I'd be lying awake at night just wondering when the rust will eat it's way through the paint:eek: in fact if you listen really close when it's quiet at night you should be able to hear it rusting... kinda like why you should never park a chevy near the bedrooms of a house, because all the rusting noise will keep you up!!! :D

:laugh:
 
#28 ·
I thought in the PNW you wouldn't hear the rust until the rain stopped but only until the moss grew over it.

On even longer consideration, the original question was the "Best" way to do it , not the fastest. If it was me and nobody was looking , the O/A torch would take care of it right quick. Like when you heat a Bolt/Nut on a car or truck after soaking with WD-40. When the flames finally shoot out of the threaded part , you know its hot enough for the impact gun.

https://www.weldingweb.com/images/smilies/biggrin.gif
 
#30 ·