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Last year, I had a big stone chip with growing rust. I thoroughly sanded it, applied primer, and painted it. It wasn't meant to look good as I just wanted to prevent the rust expansion.

However, after a year, the rust bubbled up again as shown below:

Rust bubbling up through repair

How can I eliminate the persistent rust? Should I use either of the following products before painting:

  • rust converter
  • rust remover

I'm not sure if they are good with car body paint or which one is better.

  • 1
    @Autistic, thank you for the edit and proof reading. – Allan Xu May 29 '16 at 13:36
  • I would bet you didn't eliminate all of the rust during the initial fix. Also, when you put the primer on, it needs to be self sealing primer, or you'd need sealer by itself. This is what really prevents the rust from forming again. – Pᴀᴜʟsᴛᴇʀ2 May 29 '16 at 15:31
  • @Pᴀᴜʟsᴛᴇʀ2, I used duplicolor.com/product/sandable-primer obviously did not work well. Would you be able to refer me to a few good options? I would buy whatever product that can fix this for good. – Allan Xu May 29 '16 at 17:07
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    I was hoping @JonathanMusso would show up as he's our resident expert. I'm not anywhere close to be able to give you an opinion. Hopefully someone will chime in with something for you. – Pᴀᴜʟsᴛᴇʀ2 May 29 '16 at 17:08
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So I've thought about this question for a long time now and finally decided to answer.

If you really want to keep the rust at bay, then you are definitely going to need to apply a product designed to do so before applying any cover-up paint. I believe that a rust converter product is the best option. Take a look at products like Corroseal Rust Converter Primer when shopping for a good rust converter. The Corroseal one has very high ratings and plenty of success stories.

First, sand the paint back down to the rust. Then, use a wire wheel (alternatively, you could use a stripping disk which is also very effective at removing surface rust) to remove as much rust as you possibly can. This probably won't get all of the rust, but that doesn't matter since you'll then use a rust converter product.

Find a hearty rust converter that is a rust converter primer as this will add just one more layer of protection once applied. The Corroseal product I mentioned before converts the rust and then changes to a black primer color. From there, lightly sand the black primer and apply a good primer sealer on top of it.

Provided that you spray your primer sealer evenly and it looks good when dry, you don't need to sand it before then applying your car paint on top of that. It's recommended that you paint over a primer sealer within 1-2 hours time of it being applied. However, if you miss your time window, lightly sand the primer sealer with 600 grit wet sandpaper. From there you should be able to spray your automotive paint over the primer as you did before.

Be aware though this is not a lifetime guarantee that the rust won't come back in this spot. Once rust has seated itself into metal, it usually takes a patch panel to really ensure that it will stay away. However, if you properly follow the steps on each of the products mentioned, you should be able to apply a decent paint job that will keep the rust at bay for quite some time. Best of luck with your endeavors.

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    Thank you for help. In regards to the Corroseal Rust Converter, what do you think of this article: ncptt.nps.gov/blog/… – Allan Xu Sep 23 '16 at 3:26
  • @AllanXu I believe what the article says. I've never actually used the Corroseal, I had only heard about it from others who had used it. Rustoleum carries an extensive line of products that I have always found to be of excellent quality. If the article says that the Rustoleum Rust Reformer is hands-down the best product then I would easily believe that. Nice researching before just running out and buying the product. +1 – Dalton D Sep 23 '16 at 12:35

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