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Will Flex Seal spray work to "fix" a vehicle with a rusty and pitted roof?

By "fix", I mean:

  • Keep all water out
  • Keep the rust from spreading
  • sometimes, maybe, possibly, not always - depends on the sizes of the holes / pits etc... – Solar Mike Feb 23 '18 at 10:34
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  • Keep all water out

Yes, if you use enough. Flex Seal (from my understanding), covers well and seals even better.

  • Keep the rust from spreading

Absolutely not. That's not what Flex Seal does. Rust will continue to spread unless you eliminate the rust. The Flex Seal may slow it for a time, but the rust will continue.

If you have large areas of rust, fix it correctly by eliminating the rust, either though grinding and chemical treatment or replacing the panel. Then get it painted properly to prevent it from coming back. Flex Seal is not the way to go.

  • Thanks for the answer. I contacted Flex Seal, and they recommended grinding down to bare metal and then applying the Flex Seal. They recommended not using any primers or paints before applying the Flex Seal. I'm not sure about chemical treatments. That might cause a bonding incompatibility. – RockPaperLizard Feb 23 '18 at 23:12
  • @RockPaperLizard - I'm suggesting a chemical treatment to arrest the rust ... completely stamp it out. If you don't, it WILL come back. Do as you like, obviously. Just remember, you ask Flex Seal what to use/do, they are going to suggest their product. IMHO, this is not the way to go. – Pᴀᴜʟsᴛᴇʀ2 Feb 23 '18 at 23:19
  • Do you know one or two good chemical treatments that work? On other projects, I've used several of them (after grinding away the rust first), and the rust came right back. – RockPaperLizard Feb 24 '18 at 4:45
  • @RockPaperLizard - Use something with phosphoric acid in it. Really, though, rust treatment is only half the battle. Proper finishing is what keeps it from rusting again. You need to arrest the rust, clean it thoroughly, seal it, prime it, paint it, then top coat. If done correctly, you'll get a long lasting finish which you won't have to worry about rust for a long time to come. – Pᴀᴜʟsᴛᴇʀ2 Feb 24 '18 at 12:27

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