Strange behavior with rattle can primer and neo magnets

Dirk

What kind of crazy physics do we think happened here?
I sunk neo magnets into the cab. They're covered in epoxy & spot putty and imperceptible to the eye or touch. Spraying the cabs with a fresh can of Rust-Oleum high build primer created these funny rings.

Steve_Lee

is there any metal oxides in the paint ingredients or the sandpaper you used?

hifiside

Cool least you’ll know where the magnets are for the grill.😆

Dirk

@Steve_Lee said:
is there any metal oxides in the paint ingredients or the sandpaper you used?

I would guess some amount of titanium dioxide since it's the most common white pigment? But that's not magnetic.

My theory is that the spraying of the aerosol created a static charge.

DrewsBrews

Well that is not too far off what happens when spraying powdercoat isn't it?

PWRRYD

First problem.... Rust-Oleum. Just saying

Dirk

@PWRRYD said:
First problem.... Rust-Oleum. Just saying

It's... primer. I'm probably going to sand 1/3 of it off anyway. The bar is low.

Dirk

This IS making me a bit concerned that I'm going to have to roll and not spray my top coat.

Dirk

Tell your kids about the scientific method.

So I did some tests, and @Steve_Lee, you are probably on to something. Either some metal, or some plastic / vinyl additive that generates static electricity. Or @PWRRYD is right, and the problem is in the coating manufacturer. ;-)

First of all, the cabinets were painted under midday sun, 56F, with 39% RH. A tad windy at 6-8mph, (my whole cab will need a fine grit knockdown because it feels a bit...flocked). My tests were done in my garage @ 48F / 49% RH. I don't think it's a temp thing, and probably not an RH thing.

I grabbed the glue stick and attached a 10mm x 4mm neo magnet to the back of a clean, new, note card. A shame they were all colored, so I couldn't use the moment to confirm my top coat color. But I digress. I sprayed one with the primer, and one with the intended top coat. The ring showed up heavily on the primer...but still slightly on the top coat. Hmm, okay. Darn.

Then I realized that maybe my glue stick application was perhaps an unnecessary variable. Was it soaking into the paper? Or perhaps I compressed the paper fibers with my greasy ape fingers as I was adhering the magnet.

So I did it again without the glue, because, hey, gravity does a good job of keeping the paper on top, and any small air gap shouldn't be an impediment to strong-ass little magnets.

Does not appear to be visible in the top coat sample, so that gives me hope. But something in that primer is definitely incompatible with magnetic fields.

jhollander

Maybe you can pre-separate the component by spraying through a bucking magnet O :

jr@mac

There may be a ferrous component in the primer pigment.

ugly_woofer

I've had that problem with numerous paints. I usually use extremely light coats to avoid the issue.