Touch up paint job.

I recently did some touch up paint job on my camry. I used the 3M sander pen which is made from fiberglass to remove the rust. No matter how hard I tried, I just can not remove the bottom layer of rust. Same thing on the corolla. It is kind of like the weathering steel, which will develop a protection layer after several years to prevent further corrosion. My question is Can i just leave the layer there or i have to remove it? If i have to, what can i use to remove it? Any experience?

I've had similiar problems with my Camry when touching up. I attempted to use the fiberglass pen as well, and did good for so long until it got to the bottom. I think that if you do decide to go ahead and touch it up from that layer it will eventually show through or bubble up. I ended up using a really fine grit sandpaper to remove the remaining rust, which if used very carefully, it will work effectively. Other than that, if you decide to use a rough sandpaper, you'll more than likely have to repaint the whole panel.

What is the degree of the sandpaper you used? Do u paint on the bare metal directly?

csaxon, Did u use it? how did it work?

You don't paint the bare metal directly, if you use a touch-up can with the little brush, you can buy a kit, which you can primer the metal first.

What is the degree of the sandpaper you used? Do u paint on the bare metal directly?

I used 200 grit...slowly working my way higher up to about 300 until the metal is prepped for primer.

mrtwo it's used by a lot of professional paint/body shops. It was used on my old Benz at Stewarts Autobody in Memphis and I watched detailer I know here in Cedar Rapids using it on a BMW restoration. That line of products is easy and safe to use..it really gets the rust out without harming the paint. 3M also makes a similar product but it was very agressive and caustic and expensive. I would suggest it for complete part dipping only, not spot rust.