Todays daft question. Mild steel and cleaning

[xillent]

I don't know if this is a daft question or not. When I order mild steel it often appears with a kind of black coating or oily surface. What's the best way to remove this for painting?(Particulary for larger items)

 

[tigdlo]

The black coating you are refering to is probably scale from hot rolling the steel. I use citric acid or cubitron flap or fibre discs to remove it after degreasing with brake cleaner. I used to use hydrochloric acid but have been warned about corrosion risks so no longer do that even though it's fast.

 

[Erie Fred]

I don't know if this is a daft question or not. When I order mild steel it often appears with a kind of black coating or oily surface. What's the best way to remove this for painting?(Particulary for larger items)

Are you ordering Hot Rolled ?
Or P&O ? (Pickled and oiled)

 

[BrokenBiker]

All the steel I get from brundles recently is thick with black grime...brake cleaner and some blue rag deals with it to get it clean enough to handle

 

[Maxakarudy]

If it's just the oily surface you need too remove, I use turps sub or similar slow drying thinner, the slower the solvent is to evaporate
gives you more time to soak it up with rag, fast dry solvents, brake cleaner, thinners give less time, but are fine for small areas

 

[xillent]

Thanks Guys, I've just been using a degreaser. The foamy stuff in a can.

 

[Smallfry]

Mill scale. You will need to remove it to weld, and paint does not adhere well to it either.

 

[colnerov]

I just use petrol and blue roll to get the oily residue off and a flap wheel for the mill scale.

 

[xillent]

Thanks, yes, I've been using a flap disc to weld and sometimes all over depending on the condition of the steel. I wasn't sure if that was overkill.

 

[Seadog]

I've been using a flap disc to weld

Pictures or it never happened

 

[xillent]

Now that I think about it, that explains a lot. I've been using the welder to clean off the mill scale. Maybe I've had things back to front.

 

[Smallfry]

Now that I think about it, that explains a lot. I've been using the welder to clean off the mill scale. Maybe I've had things back to front.

You CAN weld through it, once you get a spark going, but its not best practice. The weld will not be as neat, and will not be as strong as it could be.

Try it on a piece of plate, and see for yourself.

 

[premmington]

Mill scale. You will need to remove it to weld, and paint does not adhere well to it either.

+1 for the above...? Mill scale remove with gentle flap disc for MIG - MMA will burn thru and self clean it...