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I accidentally drove my car over a curb a while back. As you probably already know, the car suffered from minor scratches and dents on the bottom side, near the rear tyre. Now, I've noticed that it's now slowly developing rust on the scratched paintwork. The rust isn't too bad, i.e. the rust part still feels pretty solid.

How do you effectively deal with this kind of problem (other than telling me to drive more carefully)?

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up vote 17 down vote accepted

The best thing to do would be to sand down the rusted area until you can see the original metal and then apply a automotive primer to protect it from the rust.

If you feel pretty comfortable with a bottle of spray paint and aren't too worried about a pro job, you could then obtain some automotive spray paint and repaint the affected area(s).

One thing to keep in mind is that you're going to want to sand down the smallest area possible. When priming and painting, cover exposed surfaces with newspaper and tape it down so that you don't end up with primer or paint running on other surfaces of your vehicle.

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There are primer formulas that react with the rust so that you don't need to sand away all of it, but definitely do clean it up. I'd also recommend a wire brush (particularly a motorized one, say as a wheel on a grinder) over a sander, as it tends to get into the craters better and sand off the "high" but otherwise good metal. – Sean Reifschneider Mar 8 '11 at 7:49
What @Sean Reifschneider said + one of those primers being Brunox Epoxy I've used it personally, worked pretty well. – Slink84 Mar 8 '11 at 12:37
Do you use Acetone in removing the rust like the other top answer recommend? I have heard many times that people should get the rust totally out or it will get bad again soon. Sanding can be pretty time-consuming thing to do. – hhh Oct 1 '13 at 21:26

Napa Rust Treatment Permatex 765-1671

I used Napa Rust Treatment Permatex 765-1671 on my F-150 truck about 8 months ago and all the rust is gone! This treatment is like a grey primer. It's not pretty on a blue truck, but neither is oxidized red cancer.

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This is good stuff. I find it works better to treat the rust than to sand it down and re-prime. I can never get the sanded surface perfect enough for the primer. You do need to paint over the rust treatment though. It will allow a lot more moisture through over time vs. paint. – Brian Knoblauch Aug 25 '11 at 14:44
The affecting agent is acetone, according to specs here so basically a strong acid, not like WD40 where some petroleum mixtures (out of curiorisity). If one uses this method, one needs to make sure the metallic surface is enough thick. This bottle makes Acetone just more accessible with the gas (dimethyl ether). – hhh Oct 1 '13 at 21:22

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