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Thread: Spot Repair

  1. #1

    Default Spot Repair

    I am working on a 01 Bonneville that had an open rust spot about 1-1/2" in diameter just below the Gas door. It was also dented 1/2" deep. I prepped the area with a prewash, ground the rust to bare metal, except as I did so another small rust area began to appear and grew in size as I continued to grind. Must be rusting from the back side of the fender and is inaccesable due to an inner fender. I used Rust-Mort and treated the rust as per the directions. I was also very careful not to get any on the paint. After a full 24 hours, etching primer was applied. Next Rage Gold to fill the dent followed by S/W NP75C Ultra Fill Primer. S/W Ultra Basecoat and their new HPC15 Air-Bake Clearcoat finished the fix and it looked great! --- Next day bubbles are forming under the new paint. Now this needs to be repaired and the only other thing I can think of is I didn't use a sealer, but I thought the new 2K primers took care of that. Any comments or ideas would be appreciated.

  2. #2
    Join Date
    Nov 2005
    Posts
    39,016

    Default

    There are two things that look like they were done incorrectly...

    1. You should NOT apply etch primer over metal conditioner or conditioned metal.

    Most etch primer will not adhere to conditioned metal so epoxy primer would have been the better choice. My guess would be that the problem you are seeing is directly related to this situation.

    2. You should NOT apply body filler over etch primer.

    Filler doesn't like etch primer and it usually will not adhere properly. Again, epoxy primer would be a better choice. If I apply filler over epoxy primer (a rare occurrence) I scuff the primer with some 80 before the application of filler. Etch can go over filler but no filler over etch.

    You're a "prime" example of why I recommend epoxy primers for most beginners. Less potential disasters because of the limitations of etch primer.
    Last edited by Len; 07-11-2008 at 02:56 PM.

  3. #3

    Default

    My experience in bodywork and painting was in the south where rust was unheard of. Now, here in New York state it's everywhere! I'm far from being an expert, and rust is new to me. In hindsight I should have come to this forum first. I am still nervous about the rust working from behind the outer fender after the repair. Would you think the rust converter would stop any further rusting? I understand and appreciate your comments, but just to be sure would I be correct to fix my mistakes by -

    1. Sand back to bare metal and the rust spot from behind.
    2. Apply more Rust-Mort if necessary & wait 24 hours.
    3. Spray & sand epoxy primer to seal the conditioned & bare metal.
    4. Fill the 1/2" dent with Rage Gold.
    5. Another coat of epoxy primer and sand for basecoat.
    6. Clearcoat.

  4. #4
    Join Date
    Nov 2005
    Posts
    39,016

    Default

    1. Sand back to bare metal and the rust spot from behind.
    2. Apply more Rust-Mort if necessary & wait 24 hours.

    Sanding the rust will remove the loose material and the Rust Mort will help stabilize the rust so that it can be primed and painted. Rust Mort isn't very strong so you may need to apply it heavily but be sure to follow the directions carefully and wash it off if recommended.


    3. Spray & sand epoxy primer to seal the conditioned & bare metal.

    You can skip the first coat of epoxy primer and wait until after the filler work is finished before priming.


    4. Fill the 1/2" dent with Rage Gold.


    It's usually best to try to work out the dent before filling the surface irregularities. If possible tap out the metal but if it's not possible then filler will have to do the job.


    5. Another coat of epoxy primer and sand for basecoat.
    6. Clearcoat.

    The typical method is to apply your DTM (direct to metal) primer then apply a filling primer then guide coat, block sand then base and clear.

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