Hot Rods Mill Slag Removal ?

I believe that's what the dark gray/black stuff is on raw steel. I thought I remembered a thread on here about an easy way to remove it but my search couldn't find it. What do you guys do ?
I dressed the welds with a flap disc when I welded the caps on but thought this might might not be good for the round surface of the tube staying round if done down the length. I want to either paint or powder coat this bumper as a final finish since chrome prices were crazy.

 

Grit blasting.

 

Fastest way would be chuck it in a lathe and use crocus cloth, finish with 400 grit/scotchbrite.

 

If you are going to powder coat it, they will sand blast it first.

 

Air driven Needle chippers work well for small areas for welding.
https://www.zoro.com/ingersoll-rand...9fcScaNVzrUDQnnEWPafMaAgox8P8HAQ&gclsrc=aw.ds

 

That isn't mill slag that is from the oil in process when the tube is drawn. You get mill slag on hot rolled steel.

That said I would spin it and take a piece of emery cloth to it.

 

I was thinking I read something about electrolysis removal, but if the powder coater is going to blast it anyways. I just don't want a blasted textured surface as the final finish.

 

Let the powder coater deal with it.

 

The lathe part is right, but crocus cloth will hardly polish T. G. and P. let alone that scale.

That stuff even requires a pretty agressive emery too, I know, I had to clean that **** up for thirty years whenever a "fabricator" cut a piece of it saying "it's just mild steel".

 

I use Rust Cure to remove mill scale . It contains phosphoric acid . I found this by accident when I left a part I had sprayed with Rust cure on a piece of hot roll 16 gage . When I picked up the part , the metal beneath was shiny metal. I used it to strip both side of a 4'x 8' sheet of 16 gage. You have to let it sit on there for a while ,but it will dissolve it. Bill

 

I don't think powder coaters like tubes that are totally sealed also?