How do I fix rust spots on rear wheel arches?

[ganda1f]

The three winter months took quite a toll on my rolla's bodywork, thanks to the monumentally stupid idea of spreading thousands of tons of salt on the roads.

Summer 2009 I did a proper cleaning job on these spots, rust protective primer, and final coat with toyota paint. And a wax coat before winter. It still looked fine in november.
Here are some pics of how it looks in march 2010. Most of the miscoloration will likely disappear with a wax job, but the rust is still going to friggin be there.
Rear driver's side and close-ups:






Rear passenger's side and close-up:



Question is what can I do about it and when should I do it. Most importantly, how do I fix it in the best possible way? I don't feel like redoing the cleaning and painting every year. One or two more jobs like that and there is not going to be anything left of the wheel arches

Obviously it is not going to fall apart in a week or a year, but I much rather do something semi-simple now/soon than leave it and have to weld bodyports later on. Perhaps this is just inevitable?

I intend to keep and drive the car pretty much forever I just like it that much.

[zythr]

Sand it, prime it and repaint it. Do it as soon as you can before the rust starts eating through. In the meantime try to keep the area as free of salt as you can, especially when the temp gets above 32 degrees; that's when the salt/rust really get to "work"

[ganda1f]

That is just it. It was perfectly cleaned this summer. Bare metal, prime, paint. If it detoriorates that bad, wouldn't it suggest that it is rusting from the inside and has already eaten through to the outside?

[PhatRoyale]

I already see that the metal has started to bubble which means that it's already rusted through.

If you take a pick hammer and hit the bubbled spot, I guarantee you the metal will shatter.

It's pretty much too late to repair, unless you have access to a welder and cut off the rusted parts and reweld on new metal.

[Sine Deviance]

Yeah, if the sheet metal is rusted through the only proper way to fix it is to cut out the rusted section and weld in a patch. Then sand the seams of the patch so it's flush with the rest of the body. Then paint.

[ganda1f]

OK thanks. Do you see any point in trying to cut out the rusted part and patch it up with glass fibre and epoxy? Instead of welding, since I cannot weld myself. The rusted areas do not seem to be that big, and I can live with the patch not being completely flush with the rest of the body. Would this be any good?
Say on a scale 1(do nothing)-10(weld a patch properly).

[PhatRoyale]

Grab yourself a variable speed random orbital sander with a few different grades of sandpaper and start to sand off the rust. Chances are you'll probably hit bare metal. If you're lucky then you won't. Use a rotary tool with a grinding stone and take off the rust in the wheel arches. Stick a mirror under the fender and do the same from the inside out.

If you hit bare metal, get yourself some KBS Coatings 3-step system and do a few coats of that to ensure the rust doesn't spread any further.

Then apply body filler as needed.

But a word of caution, this might save the minor spots, but be prepared to weld in new metal in the bubbled area if this fails.

[ganda1f]

Allright, thanks. Looks like I have a project coming up I'll see if I can get my hands on a welder and practice some spot welding. Otherwise it will be glass fibre. As soon as outside temperature allows I'll get to it. Hopefully in a month or so.