View Full Version : how to remove mill scale?

02-29-2008, 01:03 PM
I got the top for my new welding/fixture table that I have been working on yesterday, 7'x3'x1/2", I am trying to clean up the surface before the leveling process begins and not having much luck. I have tried belt sanding with my Porter Cable 4x24 using 40grit. Anybody have any ideas that might work, muratic acid?

02-29-2008, 01:07 PM
what about an air powered needle scaler, its what its designed for ;)


02-29-2008, 01:23 PM
Is it just a general use table? does it need to be really really flat and level for a reason?

I didn't touch the scale on mine when I built it. As I used it (tacking fixtures and projects to the table, then grinding them off) the scale came off. Grinding off the spatter from the mig welder also took off scale.

If you really need it off, I'd hit it with a large grinder (9") and some 80 grit. Light sweeping passes.

02-29-2008, 07:57 PM
Speedy...#1..I wouldn't remove it. Spatter sticks to shiny new metal like $#it to a wool blanket. It's far easier to scrape it off mill scale.
Sooner or later that will all be gone anyway.
But if I really had to remove it..I'd run a bead of silicon all around the table edge...then pour vinegar on it and cover with plastic sheet. Let it sit overnight and you'd have a nice clean table by the next day. Mop the mess up with rags...or yer mother inlaws underwear...you'd be good to go.


02-29-2008, 09:04 PM
These work good for me. With a table the size of yours, you'll use quite a few. They wear down pretty fast but they do work. I use them mainly for surface prep before welding when I don't want to grind the surface down with a grinding disc.

McMaster Carr #4748A28, Nylon Mesh Abrasive Discs.


02-29-2008, 10:21 PM
Torker, Thanks for the vinegar tip, I will try it tomorrow. I am gonna be using this table to build cromo tubing chassis for motorbikes and other similar projects, I will be drilling and tapping holes for fixtures, I also bought a piece of 14ga. sheet exactly the same size that I will put on the table to protect it while welding. Altogether the two pieces of steel came to $450usd, more than I expected tp pay, but it is what it is.

03-01-2008, 02:47 AM
Hope you are not hoping for a really flat surface, 1/2' steel plate is like a sheet of jello, level it here and it moves there. unless you are seriously bracing it from underneath you will have trouble getting it level all over. I know it's a large area but if you can find a cast surface like an acorn plate somewhere the accuracy of your frames will be in question. My welder is setting up a from the ground up motorcycle frame shop and we are trying to find the same flat surface that won't move. same dilemma. Peter

03-01-2008, 03:08 AM
Scrap yard table from a Boring Mill or the like. I tried to figure out what to do with one of those not too long ago, but just couldn't justify it. About $0.20/lb now. Also saw a platen from a big ol' print press that might work well. It was about 3' x 5' as I recall.

As for the scale, don't sweat it. I've been working on my 4x4x1/2 fab table for several years. I weld fixtures on it all the time, knock 'em off with a hammer and grind flat. I generally "clean" it with an old cheap POS 7" "grinder/buffer" I picked up for ~$5 at a yard sale. I keep a 60 grid flexi-fiber disk (not a flap disk, but old school kinda like plastic with AO abrasive embedded) on it all the time. Just let it float over most of the surface to knock off the spatter, epoxy, whatever's on it. Concentrate just a little on the recent spot welds to level them out completely. Works well. But I've still got quite a bit of that black finish (though smooth as glass) spotted about the surface. Doesn't' bother me a bit...

03-01-2008, 08:18 AM
Flat and level is easy. Build a frame and fill it with concrete. Then cover it with steel. I left out a few steps but that's just details.


Also, if you want the sheet to stay flat then screw it on. I used countersunk cap screws on both my tables and they are pretty flat. I left the scale on and it still looks pretty good since I built the tables last year. I did a LOT of fab work too.



03-01-2008, 12:16 PM
Well, the vinegar didn't work. This morning I tried muratic acid/water mix, no luck, increased the acid to water mix, no, tried straight acid, some reaction but mostly no. I took a small scrap of 1/4" plate I had and poured straight acid on it, WOW!, cleaned it fast and good, but on the piece of 1/2" I'm using for the table it didn't do much. ??????

03-01-2008, 06:38 PM
Speedy...that's strange. I have a 12"X12" Tupperware pan with a lid that I keep vinegar in all the time. I've never had a piece of mild steel with mill scale that the vinegar wouldn't remove.
However...if the steel got fresh oil on it(from drilling lube or whatever) it wouldn't work.

03-01-2008, 08:07 PM
Torker, Nope, no oil or any other substance on it. So far I have tried,
1.- Vinegar
2.- Muratic acid, diluted and full strength
3.- Oven cleaner
4.- Paint/epoxy remover
5.- 36 grit on D/A sande
6.- Lacquer thinner

Nothing so far has any dramatic effect on this stuff. What exactly is mill scale anyway?. This has become a personal challenge.

03-01-2008, 08:10 PM
Mill scale is the oxide "crust" that is formed when they hot roll the steel.
They must have rolled yours extra hard :D
Are you sure it's mild steel?

Michael Moore
03-01-2008, 08:34 PM
I tried muriatic acid on some hotrolled steel plate the other day and had zero luck with it. Sure, you can hit everything with a disc sander, but you end up with all the little bits of pitting still retaining some scale.

I'm thinking about seeing if electrolysis has any effect on it.

What you can do on your plate for the top of a workbench is weld bolts to the bottom of it and then you can use those in conjunction with shims between the plate and bench top to do some localized pulling on the plate to level it.