Remove mill scale?

[70runner]

I have to remove mill scale from two 20' pieces of hot rolled steel square (2"x2") tube to weld/paint. Looking for an alternative to the muriatic or other acid treatments. Has anyone tried HF evaporust for removing mill scale?

 

[rockwithjason]

that won't take off mill scale. it does pretty good at surface rust

 

[Clik]

A knotted wire wheel on an angle grinder usually does the trick for me. I've wet sanded with dawn dish soap and water with good results too.

 

[HMCFab9]

vinegar is a little less caustic, but takes longer.
The only way I know of without chemicals is blasting it.

 

[lilredex]

The best solution in my book for mill scale and rust, is this type......

http://www.aliexpress.com/item/pain...asive-stripping-wheel-and-disc/924578979.html

IF you are in Canada, CTC has a set including this wheel on sale regularly for $12

 

[pepi]

A knotted wire wheel on an angle grinder usually does the trick for me.

X2 on that, very effective and moves along.




A waste of $$$ does not last :
http://www.aliexpress.com/item/paint...924578979.html

 

[A_Pmech]

You don't need to remove the mill scale to paint it. The scale is so tenaciously adhered to the steel the paint will come off before the scale.

Actually, you don't even need to remove the scale to weld it if you're using the SMAW process. Commercial quality welds are produced all day and every day though mill scale. The flux will float the oxides.

MIG and TIG require more cleaning than SMAW, but just hit within 1" of the weld with a knotted cup brush or a 40 grit flap wheel and you'll be good to go.

 

[pepi]

Mill scale is uneven and will make a paint job look the same. Paint coming off before the mill scale is the problem, painting over mill scale.

 

[70runner]

Thx all for responses. I've read where painting over the mill scale is iffy. Short of blasting I guess the knotted wire wheel is the ticket.

 

[zmotorsports]

When using hot rolled steel (which I try not to, I generally will splurge a little and purchase cold rolled) I will just knock the mill scale back about an inch or so from the weld joint to be with a flap disk or AVOS disk. Then weld it and forget it. If just looking for corrosion protection under the paint I will wipe it down with some pre-cleaner then hit it with a metal etching primer prior to some high solids MRO paint.

If it is going to be painted or powder coated of a higher quality, I will make certain to use cold rolled or P&O steel.

Mike.

 

[Jack Olsen]

Mill scale does a very good job of protecting steel. Prep the steel for paint and it will take paint well. But other than that, I would not get too aggressive. I would only worry about removing the mill scale right where you're welding.

 

[A_Pmech]

Thx all for responses. I've read where painting over the mill scale is iffy.

Not really, unless you're trying to achieve a "show quality" paint job. In that case, you should choose a cold rolled seamless product.

Every piece of Caterpillar equipment in the world is paint over mill scale.

 

[Graham08]

Another vote for just removing the scale in the area to be welded. In my experience the scale on square tubing is smooth and not that tough to remove. I like using a 3" Roloc disc on a right angle die grinder.

 

[tomsmith]

+1 on removing the mill scale where you will weld and then paint over the rest. 20' of steel is going to be extremely laborious to remove via grinding or similar

 

[dadsEH]

Belt sander works for me

 

[Stephenw]

The hot rolled tubing that I get never has what I would call "mill scale". I just wipe tubing down with Prep-All wax and grease remover.

Hot rolled plate, bar stock, and angle iron generally has mill scale. Most of it can be removed with a knotted cup or stinger brush in an angle grinder. Some steel must be hot rolled by Satan in the forges of Hell (the mill scale just doesn't want to come off). For difficult mill scale, I use aluminum oxide in a blast cabinet.

In this picture, I show hot rolled square tube on the left. It's pretty clean. On the right is hot rolled bar stock covered with mill scale.

 

[Clik]

In Baltimore the steel plant was using sewer water in it's quenching operations. Part of the green thing. That might be why some steel has a pretty nasty mill scale.

 

[kingston]

Needle Scaler

 

[sberry]

Depends how good its got to be, it I really want it off I sand it.

 

[LG63]

Another vote for leaving the scale unless you're looking for an automotive quality finish. I do think it's important to remove as much of the mill oil residue as possible. I do this by "wet" sanding, using rubber gloves (most important), a dilute solution of purple degreaser, and 80 grit waterproof grinding belt cut into short strips. This leaves the mill scale but the abrasive action coupled with the degreaser helps pull out the oils. I consider it done when I can rub my finger across the dry surface and pickup little to no residue.

 

[PCO6]

The best solution in my book for mill scale and rust, is this type......

http://www.aliexpress.com/item/pain...asive-stripping-wheel-and-disc/924578979.html

IF you are in Canada, CTC has a set including this wheel on sale regularly for $12

I wait for those sales and stock up.

I agree that some times you want to remove mill scale and others you don't. When I do the above discs work well.

 

[KenS]

Many industrial manufacturers paint hot-rolled steel fabrication with high-quality red oxide primer without removing mill scale and leave it as the finished coat.

 

[Letsgobowhunting]

Many industrial manufacturers paint hot-rolled steel fabrication with high-quality red oxide primer without removing mill scale and leave it as the finished coat.

All the Industrial Manufacuturers care about any more if profit not quality. Look at the quality of most products now compared to 10 years ago and judge for yourself.

I think the quickest way would be surface conditioning discs on a die grinder.

http://www.mscdirect.com/browse/Qui...88241716&searchterm=surface+conditioning+disc

 

[bad_idea]

Fortunately I have access to a quality sandblaster at work. I have found fresh sandblasted steel is the best surface for paint. In my experience, wire wheels are not very good at removing mill scale. Flapper wheels make the steel too smooth for paint to stick well.

 

[sberry]

Ideal is sandblasted and scuffed with scotchbrite after.

 

[goofy3392]

Not really, unless you're trying to achieve a "show quality" paint job. In that case, you should choose a cold rolled seamless product.

Every piece of Caterpillar equipment in the world is paint over mill scale.

I work for a company that builds weldments for caterpillar/ old bucyrus and we always blast before painting.

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