The tailgate on my Hyundai Pony had some bad dents, especially at the top above the handle, and a little rust along the bottom. The picture on the left below shows how it looked when I got the truck. On the right is how it looked after I stripped away the paint and straightened out most of the bad dent at the top. You can see only a little rust along the bottom...
The rust didn't look too bad but after cutting away the outer layer you can see how bad it really was...
After grinding away as much rust as I could, I used some rust remover to dissolve the remaining rust. This kind of product usually contains Phosphoric acid. .It takes a few hours for this stuff to work but here you can see it has dissolved pretty much all the rust...
I painted the inside area with some zinc paint then made a section to repair the bottom edge and welded it in. I forgot to take some pictures here as I was doing it but here you can see the new piece welded in...
On the inside edge, the lip of the repair wass folded over and hammered flat and then welded in the corners...
Next, I had to finish removing all of the dents and use some filler to make the panel straight again...
Then some primer. I used some grey 2k primer made by U-pol....
...and finally some paint. This is 2k paint in the original colour called "Jamaican Blue"...