Hi guys new to forum and to body work (tinkered a bit 30 years ago). Accountant by trade so just a hobbiest. Figured I'd post project here as I could use your help and suggestions along the way.

Have a 2005 F150 that is fairly clean but for a patch of rust on right rear wheel arch. Poked around a bit and rust seems confined to small area at bottom center of wheel arch. I cut out rust with a grinding wheel and did a quick bondo repair with rattle can primer to hold it over for a while. Decided to order a patch panel and repair it properly. Will be first time welding too aside for some minor repairs on lawn equipment and a small project. Have a 110 v Lincoln Electric wire feed welder that I recently converted over to MIG for this repair.

Anyway first up is the patch panel and first question is it better to keep repair as small as possible or go larger and replace as much metal as possible? Three sizes that seem to make sense to me are shown in tape below. I is to keep it small where damage is. II is cut about 2" outside of curved section of panel. III is full size of patch panel



I keep thread updated with progress and welcome any and all advice and suggestions. Thanks.

I would keep it as small as possible. Sand it down real good and only replace areas of rust damage. Areas with light rust can be just sanded down to clean metal again. If you do larger repair you will probably end up warping the panel a lot and making the repair harder to make a great outcome.

Thanks.

Here is a picture of original damage.



I ground down the part on lower half to clean metal and cut out the section that was rusted through



Right now it just has some Bondo filling up section that I cut out



And some cheap rattle can primer to hold it over



Came out reasonably straight for first pass



Did this a few weeks ago.

Here's my game plan:

1. Cut patch panel to desired size;
2. Use as template and trace out on vehicle;
3. Cut vehicle;
4. Clean up and repair if necessary any rust inside wheel housing;
5. Apply epoxy primer to inside of wheel housing and back of patch panel;
6. Prep back edge of patch/panel where weld will be and apply weld-through primer along edge;
7. Weld patch panel using random tack welds to form continuous weld while minimizing heat -- MIG process with 75AR/25CO2 and .024 steel wire.
8. Grind high spots on welds with 3M 3/16" x 3" grinding wheel;
9. Finish weld grinding with 3M 5"X36 grit ceramic discs;
10. Remove any high spots with hammer (and dollie if I can get it back there)
11. Seal rear weld with seam sealer if it is accessible;
12. Block panel with Evercoat Everglass short-strand filler (thin as possible);
13. Block panel again with Evercoat Rage Ultra (thin as possible);
14. Block panel again with Evercoat EverGold Putty if necessary;
15. Apply Epoxy primer and block panel;
16. Apply Polyester high build primer and block panel;
17. Apply 2K Urethane primer and block panel.

I'm using Kustom Shop primers. Not sure if I'm going to try to apply base coat and clear coat or have these steps done professionally.

Your steps you listed are correct.

Thanks.

It's on the back side that you cant see. Any thoughts on gluing the panel in ? I use 3m panel bond and also sem products with good results

Yeah, it seemed fairly solid inside when I cut out the rust but it was a relatively small hole and I didn't spend too much time looking at it. There was a piece of weatherstripping or something (noise reduction?) stuck between the quarter panel and wheel housing that seemed to have gotten wet and caused the rust out. I think the rest of the panel is tight but will take a better look when I open it up again. I prefer not to have the lap caused by glue on panel and want to butt weld it. But the issue you raise is why I'm wondering if it would be better to keep the patch panel large and replace more metal with new stuff. I realize its a lot of real estate and welding can cause its own problems but I'm going to take it slow and do my best to keep things straight. Noob at welding (as well as body work) so wish me luck, ha, ha!

I would second the advice to go with a smaller patch.
It is best to use one just large enough to get the job done rather than replacing a lot of good factory metal with a patch.
I generally cut out the rust first and see the extent of the rust underneath. That way I can increase the size of the patch area accordingly. When done make the patch panel to extend about an 1" beyond your hole in each direction and scribe, cut, trim your way to as perfect a fit as possible.
This will make your welding much easier, the amount of welding much less, and chance of warping is reduced.

Thank you, makes sense.