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Projects Getting rust off the roof

Discussion in 'The Hokey Ass Message Board' started by junkyardjeff, Mar 30, 2009.

  1. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 8,588

    junkyardjeff
    Member

    Patina is Ok but I want paint and I am trying to get the rust off the roof of a 60s truck that will be my good truck when I am done but the rust is tough,the discs I have for my DA are not cutting it and the discs for my body grinder only work for a short time so short of sand blasting the roof what have you guys done to get the rust off the roof effectively without too much work. Jeff
     
  2. dannyego
    Joined: Mar 12, 2008
    Posts: 1,387

    dannyego
    Member

    If you cant sandblast it. I would grind off everything you can. If the problem is that it is pitted I would use some rust converter. Its better to get it all off but if you cant, the rust converter stuff out there works pretty well.
     
  3. Rocks Rod & Custom
    Joined: Aug 3, 2008
    Posts: 128

    Rocks Rod & Custom
    Member
    from Raytown MO

    3M makes purple grinding biscuits that works perfect for getting rid of that scaled over rust that da paper and regular grinding discs just cant touch!!

    Hope this helps
     
  4. 53choptop
    Joined: Mar 5, 2001
    Posts: 1,203

    53choptop
    Member


  5. Squablow
    Joined: Apr 26, 2005
    Posts: 17,388

    Squablow
    Member

    If you can't sand it right off I would say it needs to be blasted, I don't trust rust converters or any of that type of stuff. But if blasting is out I would at least try the 3M "Biscuits" (we always used to call them hamburger wheels, no idea why) they do work pretty well.


     
  6. 16 or 24 grit disks to get the big stuff off...

    Find a local industrial chemical distributer that will sell you a phosphoric acid pickling or prep solution. Apply with a squirt bottle and wire brush till you get the rust removed to your liking or at least turned to a gray color. Rinse with copious amounts of water and dry well. Sand with 220 and prime with a good epoxy primer.

    If you can't find the phosphoric acid go to the local grocery store and buy muriatic (swimming pool) acid (aka hydrochloric acid or HCl) ... dilute 4 to 1... ADD ACID TO WATER... do NOT ad water to acid or you will dislike the reaction. Wear safety glasses and face shield, good chemical resistant gloves and BE VERY careful with the solution to keep it off you as it will burn skin. Spray, scrub and rinse as above... Rinse again and scrub with a Scotch-Brite pad to remove any remaining HCl and then rinse and dry again... Prime with epoxy...

    Tightly adhered rust is not a bad thing... Rust is iron oxide.. the same as the iron oxide used as pigment and filler in red primers.... Leaving a little tightly adhered rust on the surface will not start more rust unless moisture can get to the surface. The bare steel plate will oxidize just as quick as the areas with tightly adhered rust if there is moisture present.

    Coatings prevent corrosion by eliminating one of the elements needed to create a corrosion cell -- Moisture. More specifically, moisture at the steel surface. Four things are needed to create a corrosion cell: A metallic pathway, an anode, a cathode and an electrolyte. Remove any one of these things and corrosion cannot occur. Obviously the steel is the metallic pathway... But the steel is also an anode and a cathode.... That is... Due to is molecular construction there are areas that are anodic and areas that are cathodic.... Paint keeps the electrolyte (water, moisture) off the surface.

    Tightly adhered iron oxide is probably bonded to the surface better than any primer will be...

    Al
     
  7. DocWatson
    Joined: Mar 24, 2006
    Posts: 10,273

    DocWatson
    ALLIANCE MEMBER

    These things are the shit for rust, we called them spaghetti wheels! Then a rust converter, clean and prime as per normal.
    Doc.
     
  8. bretcopsey
    Joined: Feb 22, 2007
    Posts: 48

    bretcopsey
    Member
    from DAYTON, OH

  9. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 8,588

    junkyardjeff
    Member

    Can anybody post some pics of the 3M grinding discs so I know what I am looking for and if that wont work I wil try the acid.
     
  10. I don't know if it's the same as above but I use 3m purple "stripit" discs. They work great and last a lot longer than the "grey" ones I've tried. FWIW
     
  11. chopolds
    Joined: Oct 22, 2001
    Posts: 6,208

    chopolds
    Member
    from howell, nj
    1. Kustom Painters

    The paint stripper discs work, maybe a bit better than sanding discs, but are more costly. I would use a DA with some 80 grit, even though it takes longer, it's safer. I'd avoid using a grinder with rough discs (36 grit or rougher), especially if you don't have a lot of experience. You CAN do damage, both with the grinding (deep scratches) and the heat build-up from a grinder.
    After you get it all down as much as possible. scrub it with a rust dissolving compound (NOT rust converter!, that just changes it, and covers it up). As mentioned, phosphoric acid works, even vinegar works, but I'd stay away from Muriatic, it's strong, and can be more dangerous, and even the fumes can cause rusting on bare metal elsewhere on the car.
    Personally I like Dupont #5717 Metal Prep, or Picklex. They work well, relatively quickly, and leave a coating that retards further rusting, and is recommended as a base for painting over. I use red Scotchbites to scub the surfaces with Picklex until every trace of dark spots are gone. Then rinse with water to neutralize and dry it quickly.
    Stay away from sandblasting, too, as the roof is pretty flat, and may warp if the operator isnt skilled in doing sheet metal!
    Glass beading would work but the media is expensive if you can't recover it and re-use.
     
  12. 85-percent
    Joined: Apr 5, 2005
    Posts: 328

    85-percent
    Member

    muriatic acid is very powerful and hard to handle. illegal for non-professionals in some states.

    if you use it, you cannot leave any rust behind. it must be nothing but clean metal. because the acid will "stay" in the rust and cause problems later. this might be fixed somewhat if you treat with phosphoric afterwards.

    FINALLY: the muriatic vapors will cause surface rust on everything in your shop if you use it inside! I would only use that stuff outdoors well away from any steel you value!

    QUESTION:

    I get my phosporic acid via auto body metal preps as described above. Is there any supply places where you can get 'generic' in bulk - say, a gallon at a time? (I've never dealt with 'chemical houses')

    I ask because I'm cheep cheep and I dont like to pay inflated prices for repackaged stuff.

    thanks guys

    90% Jimmy
     
  13. bretcopsey
    Joined: Feb 22, 2007
    Posts: 48

    bretcopsey
    Member
    from DAYTON, OH



    x2 on the muriatic acid-nasty stuff

    I found Klean Strip brand "Phosphoric Prep and Etch" at Home Depot in the paint materials aisle $13/gallon. It can be diluted with water quite a bit and is still effetive. I used a large commercial trash can on wheels as a dip tank for my fenders. Filled the can with 3 gallons of phosphoric acid the rest with water. You can barely see the gallon jug in the botton of this picture.

    [​IMG]
     

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