Sanding large metal construction beam ?

[threesixright]

Hi All,

We have a substantial metal beam.  Its ~ 8 meters long and 250 by 200 (mm).  I want to paint it, but its a bit rusty.

What would be the best machine to use and which sandpaper would be best for the job?

My first thought was actually to take grinder with a "3M Scotch-Brite Clean & Strip Disc"  pad, maybe here are better options?

When connecting the vac, anything specific to take into account?

Much obliged!

 

[Bob D.]

Porter-Cable makes a tool that might work well for your situation. It's called the Restorer.
For a one time job this might be the ticket. If you expect to do more of this work maybe
invest in something more robust. But for the price of the Restorer it is almost a disposable
tool and worth it if it saves you even a couple hours time and your back. Cleaning up that
beam in place will not be fun.

I don't know if its a good choice for wood as it seems like it would gouge pretty easily but for
cleaning metal it seems like it could be just what you need. Not sure if its small enough to get
into the web of your beam but if it is I think it would make quick work of your task.

The beam size you gave of 200 x 250mm is this the flange width (200mm) and
height (250mm)? If yes then I think there is more than enough room to use this tool.

It does have built in dust collection. The vacuum hose attaches to the handle which forms part
of the dust collection system on the tool. So no hose hanging out the side to get in your way.

Rockler has a couple different brushes for the Restorer.https://www.rockler.com/power-tools/sanding/surface-removal-sanders
https://www.portercable.com/products/power-tools/woodworking-tools/sanders/restorer-tool/pxra2676
=393

 

[AlexThePalex]

Your picture doesn't give much detail. If the beam is all rusty, first use a wire brush on a grinder, or a flap disc with grit 80/120.

After that you can sand it with any sander you want. Start with 120, no lower or you'll make lots of scratches in the metal.

 

[threesixright]

Thanks both.

[member=60461]Bob D.[/member] looks like a nice solution.  But I'm across the pond, not sure if there is an alternative for that  :-X

[member=5277]Alex[/member] any idea which sandpaper to use? Granat?

I found a close up of the beam.

 

[Bob D.]

There are similar machines from other manufacturers. I found a few on Amazon but if there is a version
for your part of the World I don't know.

You might find something in metal fabrication or the automotive body repair business that would work.

 

[Packard]

Flap sanders are supposed to be the fastest.  Most are very expensive.  Eastwood sells one that is moderately priced.

I have never used one, but the write-ups are all in agreement that this is a very fast way to sand metal.
https://www.eastwood.com/eastwood-c...MIg7Kb4Ibg8QIVSG5vBB0nqwLrEAQYASABEgLxFfD_BwE

 

[Michael Kellough]

Thanks both.

[member=60461]Bob D.[/member] looks like a nice solution.  But I'm across the pond, not sure if there is an alternative for that  :-X

[member=5277]Alex[/member] any idea which sandpaper to use? Granat?

I found a close up of the beam.

The Restorer is a great value. Look for the B&D badged version. It isn’t “made by Porter Cable”, the inventor/developer bought a license from Porter Cable to badge it as PC in order to sell it at Lowe’s in particular. Not long after he struck a deal with B&D to do the same and get into additional stores.

The abrasives are proprietary but include wire wheels and abrasive fingers and non woven abrasives as well as conventional abrasive sleeves. The dust collection is very good.

 

[afish]

The problem with a flap disc is its going to fling "stuff" everywhere.  It looks like there is some nice finished wood all around.  If you go with a flap disc I would mask/plastic all that off.  I might be tempted to try and scrape/sand as much as I could using sanders and DE.  Then trying a chemical type rust restorer.  I have used some in the past with good results.  Im pretty sure project farm did a comparison if you want to check them out on you tube.  I would get come 3m cubitron for the paper.  Even though any sandpaper will work your mileage will very drastically when sanding on metal. 

 

[AlexThePalex]

[member=5277]Alex[/member] any idea which sandpaper to use? Granat?

I found a close up of the beam.

Any paper will do. It's not like you're going to hurt the metal. But Granat is just fine.

It is a very rusty beam. I would use a grinder with a wire brush to get all rust off the beam. Of course, if you had access to a sand blaster that would be even better. Finish with some light sanding afterwards. P180 or P240.

You might find something in metal fabrication or the automotive body repair business that would work.

I grew up in the automotive body repair business. Grinders + sanders was what we used. Or a sandblaster.

 

[DeformedTree]

I would go sandblaster.  While masking off the area to contain the mess will be a pain, it's a lot easier than trying to fit power tools into the pockets of an I beam and not be able to get all the corners and such.

Of course you could remove the beam, take it outside, clean it, then bring it back in.

 

[threesixright]

I would go sandblaster.  While masking off the area to contain the mess will be a pain, it's a lot easier than trying to fit power tools into the pockets of an I beam and not be able to get all the corners and such.

Of course you could remove the beam, take it outside, clean it, then bring it back in.

LOL. It's load bearing  The contractor thought we would case it. If he would have asked.... I was happy to pay a bit more and have it coated in the first place.

With regard to sandblasting. What would be the best media to use for this?

 

[Ron B]

What if you took a 4 1/2" grinder, put a wire brush cup wheel in it and hit it with that?  Wear long sleeves and face mask because those wires have a tendency to come out.  When everything is done there is a liquid that you can paint on it that chemically converts the rust to a stable standard. It turns the rust black, then  you prime/paint over that. You want to knock the heavy rust off, but do not need to go all the way to bare metal. I think it is a phosphoric acid solution that is used by car restorers, etc. I used it 40 years ago but don't remember on what, or if it is even around any more. I bought mine from a classified ad in Hemmings Motors.  (I told you it was a long time ago) Maybe someone else in FOG has more experience with it and can confirm this stuff works great or is snake oil. 

 

[jeffinsgf]

What if you took a 4 1/2" grinder, put a wire brush cup wheel in it and hit it with that?  Wear long sleeves and face mask because those wires have a tendency to come out.  When everything is done there is a liquid that you can paint on it that chemically converts the rust to a stable standard. It turns the rust black, then  you prime/paint over that. You want to knock the heavy rust off, but do not need to go all the way to bare metal. I think it is a phosphoric acid solution that is used by car restorers, etc. I used it 40 years ago but don't remember on what, or if it is even around any more. I bought mine from a classified ad in Hemmings Motors.  (I told you it was a long time ago) Maybe someone else in FOG has more experience with it and can confirm this stuff works great or is snake oil.

I believe you're describing a product called "Ospho".http://www.ospho.com/index.htm

 

[afish]

No its not snake oil. I have used it before.  I have found it can depend on the environment too.  If its something that is going to be subjected to outdoor environment then no its not the best solution. At that point its pretty much sandblasting.  I bought a old unisaw and the top was rusted bad.  I used a product by rust oleum that worked really good.  a scotch brite pad and the solution removed 99% of the rust.  There are others that are supposed to form a primer type coating too.  It will depend on how smooth you want the finish to be. Being indoors and in finished space I would attack it with a sharp putty knife for the big stuff and then some sanders hooked to a DE and then brush on the rust converter for the rest.  followed by some satin black   

 

[Cheese]

I’ve used a pair of cordless RA grinders to clean up a motorcycle trailer. One grinder had a wire cup wheel mounted and the other a flap wheel. Everything was then painted with POR 15.

 

[Maestronus]

+1 for grinder with a wire brush. It’s what I used for rusty I beams in my crawling space. This being the FOG you should of course get an AGC 18 with a 485099 brush. Be sure to prepare for some nasty dust.

 

[Michael Kellough]

+1 for grinder with a wire brush. It’s what I used for rusty I beams in my crawling space. This being the FOG you should of course get an AGC 18 with a 485099 brush. Be sure to prepare for some nasty dust.

Make a serious attempt to get a Restorer and a couple of wire brushes to benefit from it’s very good dust collection. The time saved in masking is worth the price.

 

[Ron B]

I believe you're describing a product called "Ospho".http://www.ospho.com/index.htm

Yes, that was the product.  I remember what I used it on-the frame of a 1964 Studebaker Champ pickup.  Being that it was a Studebaker, I was familiar with rust.  What I did held up good after being painted with DuPont Imron paint and primer.  Anyway, good to hear it is still around. 

 

[Peter_C]

LOL. It's load bearing  The contractor thought we would case it. If he would have asked.... I was happy to pay a bit more and have it coated in the first place.

Why not just leave the beam itself alone and cap it along with the pole to the ground? Seems like far less work then grinding, sanding, painting, etc. Either way overhead work is kinda miserable. POR15 could be painted on the beam if you wanted to kill the rust. Not of structural concern though. Is there a humidity problem that needs to be addressed?

 

[Packard]

Vinegar is supposed to soften and make rust easily removed and there are some pre-mixed pastes that are supposed to be even more effective.  All require mechanical removal of the remaining rust.

Also a paste of water and baking soda is supposed to be effective.  I never tried any of these. 

When the rust is gone, applying a zinc-rich oil based primer is a common practice.
https://www.google.com/search?q=removing+rust+from+steel&client=firefox-b-1-d&ei=zuLtYOD0E5Oq5NoP0uSRyAQ&oq=removing+rust+from+steel&gs_lcp=Cgdnd3Mtd2l6EAMyAggAMgIIADICCAAyAggAMgIIADICCAAyAggAMgIIADICCAAyAggAOgcIABBHELADOgcIABCwAxBDOgoIABDqAhC0AhBDOggIABDqAhCPAToFCAAQkQI6CAguELEDEIMBOgUIABCxAzoLCC4QsQMQxwEQowI6CAguEMcBEKMCOggIABCxAxCDAToECAAQQ0oECEEYAFD2xAJY0IMDYK6HA2gCcAJ4AIABgwSIAesWkgEJMTIuMTIuNS0xmAEAoAEBqgEHZ3dzLXdperABCsgBCsABAQ&sclient=gws-wiz&ved=0ahUKEwjgk6PQ3eDxAhUTFVkFHVJyBEkQ4dUDCA0&uact=5

Rustoleum makes a treatment that supposedly makes rusty surfaces suitable for paint.