Mill scale removal

[RWD3M]

Hi guys,

Just working on a small set of steel brackets to support an out door canopy and the steel I'm using has a thin layer of mill scale on it (as expected). I need/would like to remove it before welding and painting and as I've found, it doesn't respond well to a P36 pad on an angry grinder.

So I thought I'd try putting it into my little blast cabinet and unexpectedly (to me anyway) it seems to whip it really quickly and easily.Now, am I actually removing it or is it just changing colour through the blasting to make me think I'm removing it?

Before and after:

The other side, P36 pad one end, blast cabinet the other:

Yes, I know it's a little patchy, this was a very quick blast.

Is this a normal way of removing the scale?

What does the collective think.

 

[123hotchef]

I use a hot citric acid solution

 

[MetalMonkey]

Blasting it should be fine and you will have a nice key for the primer.
Vinegar also works well if you aren't in a rush.

 

[tigdlo]

If it doesn't have to be pretty I use a normal grinding disc as it's the fastest and ceramic/cubitron sanding discs if I need a good finish. I have used hydochloric acid but having read on here it can cause future corrosion problems I have stopped, need to to get some citric acid for future projects.

It looks like you have ethched the scale rather than removing it, you could concentrate on a small patch to see, I may be wrong.

 

[123hotchef]

i nutralize the citric after with bircard solutuion

 

[Erie Fred]

Hi guys,

Just working on a small set of steel brackets to support an out door canopy and the steel I'm using has a thin layer of mill scale on it (as expected). I need/would like to remove it before welding and painting and as I've found, it doesn't respond well to a P36 pad on an angry grinder.

So I thought I'd try putting it into my little blast cabinet and unexpectedly (to me anyway) it seems to whip it really quickly and easily.Now, am I actually removing it or is it just changing colour through the blasting to make me think I'm removing it?

Before and after:

View attachment 458879

The other side, P36 pad one end, blast cabinet the other:

View attachment 458880Yes, I know it's a little patchy, this was a very quick blast.

Is this a normal way of removing the scale?

What does the collective think.

Yup, done it many times.
What abrasive ?

 

[RWD3M]

It looks like you have ethched the scale rather than removing it, you could concentrate on a small patch to see, I may be wrong.

This was my concern.

I'm probably going to try a bit more as I've just given the blast cabinet a good going over!

 

[DickyDoDah]

Soaking the steel in distilled white vinegar works really well but does take time.

 

[E T]

Mill scale removal?

These.

 

[Richiew]

They are great but expensive and disintegrate on sharp corners. If someone else is paying they are ideal.

 

[morssdn]

Another vote for citric acid, also works on zinc coating like Zintec.

 

[RWD3M]

Mill scale removal?

These.
View attachment 458916

I'll confess, I have a couple of those somewhere but hadn't tought to try them. If I can find them, I'll have a go tomorrow.

 

[Erie Fred]

Mill scale removal?

These.
View attachment 458916

They don't "dig deep" into crevices, blasting does.

 

[Erie Fred]

This was my concern.

I'm probably going to try a bit more as I've just given the blast cabinet a good going over!

I find straight on nozzle angle is best for scale.
Scale is glass hard, you don't want to ricochet off it.