Instructables

Step 3: Grind Some More

After I got all I could with the sanding wheel, I changed over to a metal grinding wheel. When using this, be super careful because these can do a lot of damage. I worked really slowly so that I could get a nice finish on the metal. It was really good for taking the thick rust off and getting into those pits.

After 99.9% of the rust was removed, I sanded by hand (with 120 grit 3M Sandblaster sandpaper) to get a nice smooth metal surface.

If I wanted, I could have used Bondo to even out some of the dents, and fill the space where the paint is gone
bluebelle7 years ago
i was just wondering what to do if the rust is all the way through. can you use bondo for that? the spot is about 14 cm by 8 cm.
For holes, you can use a backing material for Bondo to stick to. It is Bondo brand wire mesh that has self adhesive glue on back to keep it in place. You can use scissors to shape. Just follow instructions on the package. Prime and treat the back side of the patch if you can.
By a tube of rust converter. It converts iron oxide back into a quasi metal. It is a good idea to use it on any rusty area that you are not going to physically cut out and weld a new patch back into. If you don't the rust will most likely come back fairly quickly. Rust is like cancer, even the smallest amount of rust can turn into a horrible tumor. For instance before doing this step of the instructable I would still use rust converter to ensure there was absolutely no rust left. It isn't all that expensive either so it is a worth while investment. Hope this helps.
correction "Buy a tub of"
you don't actually need much the rust converter stuff is pretty thin and goes a long way