Removing lots of mill scale. Best mechanical method?

[Iron Beaver]

I have to rustproof a roof made out of 3/16 A36 plate. This plate came covered with what I assume is mill scale, a gray surface that resists rust about 10% better than shiny steel. I have to get this off before painting. I'm debating between two different methods, both pretty expensive

1) Get a needle scaler and use it
2) Get a bunch of these: https://www.zoro.com/walter-surface...5-in-thick-silicon-carbide-15l863/i/G3120306/

Any ideas? I haven't painted a lot of my projects because I live in a super dry climate, but this one really should be rust proof.

 

[BD1]

I have to rustproof a roof made out of 3/16 A36 plate. This plate came covered with what I assume is mill scale, a gray surface that resists rust about 10% better than shiny steel. I have to get this off before painting. I'm debating between two different methods, both pretty expensive

1) Get a needle scaler and use it
2) Get a bunch of these: https://www.zoro.com/walter-surface...5-in-thick-silicon-carbide-15l863/i/G3120306/

Any ideas? I haven't painted a lot of my projects because I live in a super dry climate, but this one really should be rust proof.

No idea how this got posted ,sorry. Please see next post.

 

[BD1]

This would really do the job. I wanted the Metabo but it was $800.00 and Eastwood was $200.00 with a three year warranty. It does a great job and has a variety of wheels avaiable.
They even have 1'' wide ones used with spacers which is perfect for my horseshoe artwork and narrow pieces.
It's variable speed too. The rusted sheet is before and after cleaning to make the holder for the tool and drums. It's similar to what Eastwood sells one but mine holds more. This was using the 80 grit stripping drum and not their heavy duty one which i did buy.
They have it on sale now, https://www.eastwood.com/eastwood-contour-sctr-scale-and-rust-stripping-drum.html $27.97 areal deal
The 80 grit is on sale too. https://www.eastwood.com/eastwood-contour-sctr-scale-and-rust-stripping-drum.html $16.97
Dam, I'm gone have to spend money now, Thanks LOL.

I got it for $179.00 on sale. I signed up for their emails and got a 10% off code, Which really helps. Sometimes they offer free shipping or a free with a $50.00 order. Shipping always changes and I get emails on that too.
It is definitely worth the money for me.

Eastwood CONTOUR SCT® - Surface Conditioning Tool

Multiple Tools In One! Removes Rust, Paint, Body Fillers Conditions Metal so it is Ready to Paint Buff Metal to a Mirror Finish Professional Grade Backed by a 3 Year Warranty US Patent #D814,261

www.eastwood.com

Search results for: 'SCT drums'

The Eastwood Company provides unique automotive tools and supplies, as well as expert advice and solutions, for the classic car and hot rod enthusiast. Visit us online today.

www.eastwood.com

 

[GaryM909]

I would try using fibre discs. The 5" ones are quite inexpensive. I have some 9" ones that work well for large areas but you need a 7-9" grinder.

 

[Kenstone1]

Here's both mechanical and chemical ways to remove mill scale:

https://www.youtube.com/results?search_query=removing+mill+scale+from+steel

It seems white vinegar is the safest chemical to use (I've used it) but I'm thinking that roof is too big to be submerged.
If it's flat/level you could create a duct tape dam around the perimeter and flood it with vinegar.
If it's NOT flat, you could cover it with rags (old blankets?), soak that with vinegar and cover that with some black plastic sheeting.
Time is your friend here, so just wait for the vinegar to do it's job, and let it soak while keeping it wet.
No labor or additional stripping tools needed...
Any mechanical method would be way more labor and tool intensive.
jmo,

 

[csp]

How big is this roof?

 

[Bodj Built]

Vinegar works well, but flash rust is a big issue that I've found when using it.

 

[metlmunchr]

Got a 7" or 9" grinder? If so, get a coolie hat grinding wheel from most any welding supply house. Coarsest one they stock. A coolie hat wheel allows you to set the wheel flat on the metal and only the rim of the wheel touches due to the shape of the wheel. They work well for getting rid of scale and as they wear they continue to contact only at the rim. Cost around $15 apiece last time I bought one. For normal thickness scale, one wheel oughta easily take care of a couple 4x8 sheets. The main thing with removing scale is to be as aggressive as possible. You can use a flat wheel on a side grinder and because the force is spread over a large area, all the wheel does is mostly burnish the scale and make it shiny. At that point, it becomes about twice as hard to remove because the wheel just skates over the slick surface.

 

[claymont]

Why not just use a 'rusty metal primer'?

 

[Iron Beaver]

This roof is made of 4 4x8 sheets, so 128 square feet. The sheets have been bowed so they are about 8" higher in the center. This makes using liquids rather difficult.

A buddy suggested sand blasting. I'm looking in to that, unfortunately the only media I can find is coal slag and I won't use that stuff.

 

[king nero]

the 3M purple or blue sponge looking discs. Scotch brite? ideal for a 5" grinder. I'm a big fan of those

 

[PCustoms]

Post a pic?

I've seen a lot of structures get an acid wash to get uniform rust. It would take a LONG time to rust through 3/16 out in the open.

 

[Walkers]

No reason at all to remove it if all you are doing is painting it. Use a cup wire wheel and remove anything loose and then prime and paint.

 

[californiamilleghia]

How long do the eastwood stripping drums last ?

and are they a generic drum if eastwood stops selling them ?

Thanks

 

[BD1]

As for lasting, it depends on use and choosing the right drum for what you're working on.
The variable speed helps too.
The drums are the same as the Metabo ones and the tools they sell on Amazon.
Eastwood has had the best prices.
I bought a bunch when they had them on sale.
Signing up for emails helps. I got a $10.00 off and free shipping on $50.00 or more purchase.
I like the finish it leaves compared to swirls with using a 4 1/2" disc.
Each tool has its place and for $200.00 it's worth it to me. The Metabo was $800.00, too much for a part-time use tool.

Amazon.com : burnishing wheel

 

[Bodj Built]

I bought the craftsman version on sale at lowes for $40. It's literally still in the box, simply because I cringe at spending $40+ for consumables

 

[Jlarson]

We'd just knock any loose stuff off and coat it. If I really wanted to take it all off we'd blast it, typically on steel structure we use sharpshot media.

 

[Iron Beaver]

No reason at all to remove it if all you are doing is painting it. Use a cup wire wheel and remove anything loose and then prime and paint.

I thought that mill scale would cause galvanic corrrosion under paint and then eventually flake off ruining the paint job

 

[wrenchguy]

No reason at all to remove it if all you are doing is painting it. Use a cup wire wheel and remove anything loose and then prime and paint.

This.

Here's a 14gauge hood i formed, some scale broke loose at bend points. Wire wheel it all and prime. You will not see any loss after painting.

 

[PCustoms]

I thought that mill scale would cause galvanic corrrosion under paint and then eventually flake off ruining the paint job

Galvanic corrosion requires dissimilar metals. Pretty sure the mill scale on a sheet of steel is close enough to steel you are good.

 

[sqznby]

I'd leave the scale as well. Finish what is exposed, prime then paint.
Otherwise, a burnishing tool is the way to go. It will make quick work of this and will give an even finish in the end.
Properly prep it and get a quality primer and paint and you should be good to go.

 

[mikegt4]

I bought the craftsman version on sale at lowes for $40. It's literally still in the box, simply because I cringe at spending $40+ for consumables

Same here. I got some "46 grit rust/paint remover" wheels from the original manufacturer of the Craftsman and Porter Cable Restorer. I bought the tool to strip rust and mill scale from an auto rotisserie that I built 10 years ago but never painted. The Restorer tool stripped everything down to bare metal very easily. These photos show what took maybe 10-15 seconds per part. Some had more rust, others had more mill scale, either way the parts cleaned up even faster than I had hoped for. I also have a Sunux SX8200 that uses the same abrasive in a narrower wheel for getting into tighter places.

Restorer Tool Accessories for All Brands - Buy Direct

Restorer Tool Accessories | Attachments and accessories for every model and brand. Shipping is free within the USA on orders over $100

www.restorertools.com

https://sunextools.com/products/surface-blaster-kit/