Thread: Removing Mill Oil

Tweet

I'm getting ready to spray my car with epoxy primer and realized when I got it up on stands that the underside of the subfloor still has a lot of the mill scale(I think it's called) on it. Is there a chemicle that will remove this before painting or do I have to grind it all off. I can only hold my arms above my head for so long before I'd give up and just paint it.

Sean

It can be a real pain to remove...........some of it is easier than others to remove, but none is real easy. No chemical will touch it so you either have to sandblast (my favorite way), or grind it off. What we have found that works pretty well are those Norton black or blue "rice cake" paint removal discs that are either made for a regular grinder 5/8 thread, or the ones that go into a 1/4 inch air grinder chuck. You will chew up a bunch of them, but they are worth the $ 8 or $9 each price in the amount of sweat they save doing it any other way. Even Home Depot carries them, as does Lowes. The black ones are more coarse and cut faster, but the blue ones are ok.

We like to remove the scale from the entire piece of steel BEFORE we weld it in, much more accessible that way, but it is a double edged sword. Once the scale is removed the piece will surface rust very fast because the protective coating is gone. On small pieces I toss it into the blast cabinet and it cleans up pretty quickly, but on large pieces we just lay it on the welding table and grind it off with one of the rice cakes I mentioned. Regular grinding discs don't seem to touch it and just scar up the metal, whereas the rice cake ones don't dig into the steel. Once the scale is removed something like Picklex20 wiped on will help to slow down the surface rust, as will wearing gloves and not touching the bare metal while working on the car.

Don

Have you ever tried the regular Picklex? I read that that will work but I'm not even sure where to buy it in town here. I might just start sanding like you said . I could use my siphon sandblaster but that makes such a mess for just four panels I have to do. Now I know why all your parts are so nice and shiney when you weld them on.

Sean