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Thread: Spot rust repair 2012 GMC 2500HD

  1. #1
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    Default Spot rust repair 2012 GMC 2500HD

    Well I have dreaded rust spots coming through the paint right above the wheel arches on the box sides. I understand this repair procedure will not last forever but I want to get another couple years of no rust visible I hope.

    Here's what I have gathered for a repair plan so please do critique it as I am that newbie I will be using aerosols for the majority due to the small areas. I will use my Father-in-law's FinishLine gun for clear coating the whole panel.

    DA down to bare metal (40 or 80 grit)

    Spot sand blast (I *think* the neighbour has one I could borrow)

    Spray with aerosol 2K epoxy - I have easy access to SprayMax products local to me
    - Do I do one or two coats?

    Body filler work - My Father-in-law has some Evercoat Lite Weight and Evercoat Metal Glaze he can give me for free just need the hardener, so hopefully one of these is worthy for use

    - Do I need to scuff the epoxy if I'm in the recoat window?

    Guide Coat

    Block sand to 150 or 180

    Final bodywork touch-ups with filler/glaze

    Guide Coat

    Block sand to 180 or 220

    Spray another coat of epoxy OR should I go I now spray with aerosol 2K primer?

    Sand with 400 or 600

    Spray aerosol basecoat and blend out 3 coats

    Spray whole panel with clear coat
    - Any recommendations for clearcoat this repair that I will spray through the Finishline gun?

    Wet sand, and polish

    I'm sure I've probably made some critical errors, but please do critique and I won't take it personal. Lol. If money wasn't so tight, I'd get a bodyshop to do this work for me.

    Thanks!
    Last edited by SheeB; 04-19-2019 at 11:06 AM.

  2. #2
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    Default

    Putting body filler over a hole that can get wet from behind will probably last until the next rain storm. Check out a longer lasting method HERE.

  3. #3
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    Quote Originally Posted by Len View Post
    Putting body filler over a hole that can get wet from behind will probably last until the next rain storm. Check out a longer lasting method HERE.
    When I sand thru to bare metal I did not see a "hole" at all.

    I was told by the GM dealer (I don't typically trust them much) that the spots of rust that started were apparently a production defect. The primer of the panel was compromised by sparks during the panel passing along a tack welding station during the assembly line paint process. Myth or fact? I'm not sure.

  4. #4
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    Default

    LOLLLLLL....

    that is a beautifullllll lie ...i will actually use it now, sparsk causing rust over wheel arches ..

    this is a horrible lie it is a faulty design for the lsdt 20 years, they dont care about customers...

    i have had abouy 10-15 rust repair estimates on Detroit made trucks, all makes and models in the last 2 weeks, whem i tell people it costs thousands to fix, they think i am bullshitting...

    Now , i cannot rememeber if GMC has thst glue, sponge, foam material betwen outer snd inner wheel arches panel

    you can check it out for yourself, reach behind upwards snd see if you csn feel foam btw those things...

    this area on all trucks CANNOT be successfully reoaired by using fiberglass or body filler...

    it is exposed to rain, dirt, salt , moisturr from inside, it absorbs all of thst, once it does, even if you put oil, rustrpoofing ovet itr, it will seal moisture and rust and it will still corrode it....

    i refuse to do it, it has to be cut out and repaired woth new metal, like Len said, it costs a lot., people dont want to pay, and i dont cheat with fiberglass...

    now i think some GM models dont have this foam material behind, if yours doesnt,then u might be lucky...

    you must clean all dirt and debris behind wheel arch, with air blow gun, let it dry, clean iy again, then spray some rustproofing paint, primer, then do some body work outside, adn the rusproof with oil...

    and it might work if you are lucky..

  5. #5
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    Well I guess I shouldn't ignore the inevitable and will just let it rot some more and save up the $ to get new boxsides done at a professional bodyshop.

    Sorry for the thread, feel free to delete it Len.

  6. #6
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    Mar 2007
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    no, you asked the right question, it is just the way dealeship lied to people...

    my honest advice is for you to consider the "numbers", investement into a truck vs whst you get back..

    if you will sell it, people would rather see original panels with all the rust and dsmage then something that is just covered up..

    if you plan on keeping it, see if you can get a box with same color from South of USA where there is less rust or no rust..here in Ontario, there are shops and yards that specikialize in such business.m.

    in the mean time, you can clean debris and dort behind if there is no foam, glue, let it dry well, them rustproof it and it will help somewhat..

  7. #7
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    Quote Originally Posted by baubau View Post
    no, you asked the right question, it is just the way dealeship lied to people...

    my honest advice is for you to consider the "numbers", investement into a truck vs whst you get back..

    if you will sell it, people would rather see original panels with all the rust and dsmage then something that is just covered up..

    if you plan on keeping it, see if you can get a box with same color from South of USA where there is less rust or no rust..here in Ontario, there are shops and yards that specikialize in such business.m.

    in the mean time, you can clean debris and dort behind if there is no foam, glue, let it dry well, them rustproof it and it will help somewhat..

    Well I plan on keeping this truck till it dies as it just had the head gaskets done not 6 months ago, so the mechanical side should be rock solid.

    I'll Google for a replacement box of the same colour (couldn't care about scratches) as long as the rust is not present.

    I'll pull off the tonneau cover and see if I can get the pressure washer back in there via the stake holes and remove the tail lights and try and clean it out some. Then let it dry and spray it up with rustproofing.

  8. #8
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    Default NO!

    Quote Originally Posted by SheeB View Post
    Well I guess I shouldn't ignore the inevitable and will just let it rot some more and save up the $ to get new boxsides done at a professional bodyshop.

    Sorry for the thread, feel free to delete it Len.
    No need to delete your concerns. Your sharing helps others as well as yourself in this common problem.

    The area of your concern has the outside quarter panel you see AND an inner panel tack welded to it. UNFORTUNATELY the factory uses a foam type material between the inner and outer panels. These foam areas hold water and debris and this is what causes rust (then rot) of happen.

    There ARE 2 drain holes at each end of the wheel well opening. They get plugged pretty easily but can be kept clean and open.

    'baubau' explained what's going on in that area. I DON'T buy what the dealer told you either.

    SUGGESTION: Going forward, if rust & rot happen in the lower section of the wheel well, you could grind and or cut it out. Clean the metal well on all sides and rust proof. You could then install OEM wheel well FLAIRS that were common on this type truck. You can finesse what I said as you see fit. Keep us posted.

    Henry

  9. #9
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    I have a couple suggestions. Where that rust blister is/was take a sharp metal object like a sharp ice pick and push with light to medium pressure in the middle of that rust spot. If the sharp metal tip makes a hole then you have a rust through problem. If the ice pick doesn't go through then you have surface rust problem. If it's surface rust then I personally prefer to sandblast any rust down to clean bare metal. Sanding will not remove rust in the small rust pits. And rust is like cancer, if it is completely removed then it will get worse.

    Those are your two main options going forward. IF its is indeed a rust hole then it is only the tip of an "iceberg" with other spots getting ready to create more holes. After many years of doing this work professionally -- if you have rust holes starting around a box side wheel well then either you replace the whole box side (expensive = $1,000+ for just one side). An alternative I like is replace the whole box with a rust free box from down south or out west. There is a one more alternative and that is to put fender flares around the wheel opening which will hide the rust for upwards of 5 years before it starts getting visible rust around the fender flare. In that upwards of 5 years you have plenty of time to come up with a rust free replacement box.
    There are paintable fender flares available that range from nice looking to really atrocious. You pick which ones look good to you.

    My experience with welding patch panels on Truck box sides here in Michigan is a waste of time, labor and money for the most part. Replacing whole box side with full quarter panels is a long term repair but it's almost always cheaper to buy a whole rust free box. The main problem with welding in patch panels is you patch in fresh metal in some spots but it's guaranteed rust is going to come through in other spots.

    If you don't want to do the job right then fender flares "can be your friend" (for several years) LOL

  10. #10
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    Default Great one Phil...

    Quote Originally Posted by Phil V View Post
    I have a couple suggestions. Where that rust blister is/was take a sharp metal object like a sharp ice pick and push with light to medium pressure in the middle of that rust spot. If the sharp metal tip makes a hole then you have a rust through problem. If the ice pick doesn't go through then you have surface rust problem. If it's surface rust then I personally prefer to sandblast any rust down to clean bare metal. Sanding will not remove rust in the small rust pits. And rust is like cancer, if it is completely removed then it will get worse.

    Those are your two main options going forward. IF its is indeed a rust hole then it is only the tip of an "iceberg" with other spots getting ready to create more holes. After many years of doing this work professionally -- if you have rust holes starting around a box side wheel well then either you replace the whole box side (expensive = $1,000+ for just one side). An alternative I like is replace the whole box with a rust free box from down south or out west. There is a one more alternative and that is to put fender flares around the wheel opening which will hide the rust for upwards of 5 years before it starts getting visible rust around the fender flare. In that upwards of 5 years you have plenty of time to come up with a rust free replacement box.
    There are paintable fender flares available that range from nice looking to really atrocious. You pick which ones look good to you.

    My experience with welding patch panels on Truck box sides here in Michigan is a waste of time, labor and money for the most part. Replacing whole box side with full quarter panels is a long term repair but it's almost always cheaper to buy a whole rust free box. The main problem with welding in patch panels is you patch in fresh metal in some spots but it's guaranteed rust is going to come through in other spots.

    If you don't want to do the job right then fender flares "can be your friend" (for several years) LOL
    Your first paragraph and let's see it again:

    "Where that rust blister is/was take a sharp metal object like a sharp ice pick and push with light to medium pressure in the middle of that rust spot. If the sharp metal tip makes a hole then you have a rust through problem. If the ice pick doesn't go through then you have surface rust problem. If it's surface rust then I personally prefer to sandblast any rust down to clean bare metal. Sanding will not remove rust in the small rust pits. And rust is like cancer, if it is completely removed then it will get worse."

    So many times I think what you are suggesting because it is FACT. I thought of this very thing looking at houndog's roof (in another thread) with the black in the pours of where the rust surface was.

    What we both are describing can be confusing to many if not 'probed' as you suggest. Many times I have done this only to find a HOLE IS HIDING behind that black pit mark area.

    Glad you brought this challenge up and only hope many will remember it.

    Henry

  11. #11
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    Phil, you know what works good when you have rust around the box wheel openings is to replace the entire side panels. You know that when you do a patch that moisture will collect behind the repair and cause the seams to fail but when your seam is high and the complete side is replaced it's like replacing the entire box. I've recently decide not to do anymore patches around those back wheels because they don't last long enough while replacing the entire side metal is like starting new again.


  12. #12
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    Apr 2019
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    Ottawa, Ontario, CANADA
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    Default

    Quote Originally Posted by Henry View Post
    No need to delete your concerns. Your sharing helps others as well as yourself in this common problem.

    The area of your concern has the outside quarter panel you see AND an inner panel tack welded to it. UNFORTUNATELY the factory uses a foam type material between the inner and outer panels. These foam areas hold water and debris and this is what causes rust (then rot) of happen.

    There ARE 2 drain holes at each end of the wheel well opening. They get plugged pretty easily but can be kept clean and open.

    'baubau' explained what's going on in that area. I DON'T buy what the dealer told you either.

    SUGGESTION: Going forward, if rust & rot happen in the lower section of the wheel well, you could grind and or cut it out. Clean the metal well on all sides and rust proof. You could then install OEM wheel well FLAIRS that were common on this type truck. You can finesse what I said as you see fit. Keep us posted.

    Henry
    Thanks all for the replies and insight!

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