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Thread: Refinishing rusty trailer - grind or sand paint?

  1. #1
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    Default Refinishing rusty trailer - grind or sand paint?

    I'm refinishing the outside paint on my AeroTow utility trailer.

    See my "Trailer of Mystery" thread for what it is -
    http://www.woodenboat.com/forum/show...hlight=mystery

    Wood refinishing I know, but stripping and repainting metal is not my strong suit.


    I plan on doing a partial paint removal, treat the rusted areas with Ospho, then prime and paint with Rustoleum spray primer/paint. I'll probably do a light sanding on most of the exterior where it isn't rused to get a good bond with the new paint.

    Question 1 -- should I use a paint stripper to get the paint off in the rusty areas? I'm concerned about it washing off during the rinse/scrape process and impacting the rest of the good paint.

    2. When I sand the paint and rust, I gradually get through the paint and primer (50-grit paper) and get bare shiny metal. But when I use an angle grinder with a braided metal wire wheel, it seems to lay down a layer of dark material over the metal. Is this melted paint combined with metal from the wire wheel, or ??

    Bright bare metal on sanded area-


    Dark coating on grinded areas -
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  2. #2
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    I cannot tell if that's aluminum or galvy. Either way the wire wheel is not the best idea. Try a flap disc 80 to 120 grit on slow speed. Feather the layers back, prime ,wipe with isopropyl alcohol,then paint.

  3. #3
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    The trailer body is steel. I've removed the bolts holding the hinged lid in place, so that I can move it to a work table outside and use paint stripper on the top of it without dripping/rinsing it all over the lower part of the trailer body. The interior paint is fine except in the front bottom part of the front wedge box.

    Is it common for the braided wire wheels to leave a metallic / polished coating on whatever surface is being abraded? I noticed the same thing while grinding 80 years of paint off the concrete porch steps.

    I'll try the flap wheels as well as the paint remover unless others chime in with opposing advice.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  4. #4
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    Try to rent or borrow a sand blast attachment on a pressure washer. That will shift any corrosion. Then you can feather the edges of the surrounding sound paint whichever way you prefer.
    It really is quite difficult to build an ugly wooden boat.

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  5. #5
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    It may not be paint at all...
    powder coating is common for that type of sheet metal
    sandblasting will warp the heck out of it
    Ospho and repaint is probably the most practical solution

  6. #6
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    Treat the rusty areas with a 'rust remover'. Actually it converts the rust from iron oxide to iron phosphate (phosphoric acid). Stuff works great. Otherwise the rust may bleed through. I had to do this a number of times on the garage door that the previous owner never painted. The Plasticolor brand I find to work the best.

  7. #7
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    I'm finding that repeated treatment with paint remover gel seems to work the best. Once the paint is removed, will paint rusted areas with Ospho, an acid rust-remover.

    Still don't quite understand why the braided wire wheels leave such a strange coating... TylerD's suggestion of the flap disc seems to be the best so far at exposing metal without blackening it.

    I had to use an angle grinder to remove the rusted bolts holding the tapered front box to the frame, sanded the paint off and treaded the bottom with Ospho. Will see if the wife's stainless steel shop can do anything with the rusted-through bottom, or I can replace with a sheet of ply.
    Last edited by Thorne; 11-16-2008 at 10:55 PM.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  8. #8
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    That doesn't look too bad. Second the rec. of a converter for a primer. I've used one called POR for similar situations. You don't have to get the last smidgen of rust off. A friend across the alley where I lived in Baltimore turned me on to it. He was in mid-restoration of a Model A coupe, body off, the whole deal, and he swore by the stuff for rusty bits. I've used it for car body stuff, and as long as it's top coated it works well.
    So many questions, so little time.

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    Default Re: Refinishing rusty trailer - grind or sand paint?

    The POR , like POR 15 which I use for old cars, doesn't have UV inhibitors, at least the black color can sez it's not for sunlight areas. Most folks use it for car frames and underside areas. They may have some that has UV protection though.

  10. #10
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    Jake is right, I think the coating is powder coating, not regular paint. Paint remover is NOT removing much of it, even with multiple attempts and heavy layers of the remover, plus scrubbing with wire brush and scraper.

    Any suggestions for removing powder coating from steel? I can't just glop on the Ospho or POR, as the rust blooms are beneath the powder coating in some spots, not just where the coating has been scratched or worn through.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  11. #11
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    Like I said, flap disc is the best for that job. Find a grit that doesn't clog and I am guessing 60-80. Run at slow speed. Most welding suppliers have them right on hand. You have to feather it out for best results.

  12. #12
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    Do they make 'em for angle grinders, or only for drills? And is there really no way to chemically remove powder coating easily???
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  13. #13
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    If the powder coat is that well adhered why do you want to remove it? Treat the rusted areas and feather the repaired areas in with the old powder coat with a good quality high build auto primer and then paint the whole thing.
    Tom

  14. #14
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    Well, the rust seems to be forming under unbroken sections of powder coating, so I thought that as long as I had the durn thing apart and was grinding, scraping, and painting it -==- might as well do it right. Really don't want to fix parts of the finish and have others pop up mid-winter....
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  15. #15
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    Quote Originally Posted by Thorne View Post
    Do they make 'em for angle grinders, or only for drills? And is there really no way to chemically remove powder coating easily???
    Yes but thats high speed. They will foul in short order. A 1/4 drill will work fine.

  16. #16
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    Default Re: Refinishing rusty trailer - grind or sand paint?

    I may try chemical stripping with gasket remover, but currently am using a beltsander for the high bits, angle grinder with wire wheel for the low bits.

    http://www.choppersurplus.com/global...ercoating.html

    http://www.powdercoatingonline.com/h...entkleene1.htm
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

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