Removing Mill Scale / Priming over it.

Chad.S

Chad.S

Oldtimer
Does anybody have any tips on how to remove the mill scale that comes on plate steel. This stuff seems as tough as nails and I have never had a good solution for it.
​Can it be sanded and epoxy coated with success?

It's a big part so soaking it is kind of out of the question.

I tried sanding it but with little to no success.
 
One time I had to use a Snap-on wire brush tool. The one that has the very stiff wires like in a belt, I don't know the name of it.

Anyway, it's the only damn thing that worked well enough, took forever.

Make sure to wear some good filter respirator , I didn't and was coughing up a lung the next morning.
 
Sandblasting is the only way I know , and as it is a controlled form of rust, I would never apply anything over it if you want it ti last.
 
The mill scale on hot rolled steel is a PITA. That disc Chris linked to looks interesting, regular sanding discs end up clogging up and glaze it. I tried acid on small parts, worked but I wouldn't recommend that to an enemy, and you said the part was large. Blasting seems to be the way to go if possible to really get it all off. Recently did some small parts that fit in the blast cabinet, the mill scale acts like a mask and where it isn't cuts in more and the pattern is still there when done. I guess it depends on what the part is and what you expect from the finish. I have left it on, solvent cleaned and painted over it with decent results on some outdoor fabrications, but I wouldn't do that on anything that rates a top shelf finish.
 
I've heard of some using muriatic acid to remove it-do it outdoors though and stay upwind. If you texture it with a blaster or sanding I've seen no problems with apply epoxy over it. It is hard stuff though-might be heat tempered from the manufacturing process.
 
always a better choice to use cold rolled steel if you can get your sizes so you dont have to worry about it.. Wire brushes will work, its best to get the flat wheels instead of the cup wheels since you can reverse the wheel when all the wire turns down to the clockwise side. Otherwise we usually just use the 24 or 36 grit discs to grind it all off.
 
If I absolutely have to move it outside to blast I can but I have to completely assemble the suspension. get it outside, take the suspension back off to blast it, put it back together to move it back it​That's quite the task to get rid of some mill scale. but I've had to do worse..
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Chad.S said:
If I absolutely have to move it outside to blast I can but I have to completely assemble the suspension. get it outside, take the suspension back off to blast it, put it back together to move it back it​That's quite the task to get rid of some mill scale. but I've had to do worse..
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Chad, They work pretty good and last a good while. If you don't have to large an area would definitely be an alternative to media blasting. If you can get some of the very hard black open fiber discs for a 4 1/2 inch grinder they work well too.
 
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