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Old 01-03-2021, 10:40 PM   #1
Tim Ayers
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Default Best paint for painting over rust

While I have the body off replacing some rivets, I thought I'd also paint some areas underneath. Body is original and I don't want to blast or remove whats there. I just want to protect it from that horrible snow melting brine they put down in the tai-state area.

What's the go to product these days? I've used Por 15 in the past.
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Old 01-03-2021, 10:53 PM   #2
1937sedandelivery
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Default Re: Best paint for painting over rust

POR-15 is my paint of choice. It has worked out nicely for several of my cars that had rusted floor, etc.
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Old 01-03-2021, 11:24 PM   #3
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Default Re: Best paint for painting over rust

The POR-15 I painted the underside of my car with in 1988 is still holding up fine. That's because it's underneath, out of UV rays which will make it deteriorate quickly.
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Old 01-04-2021, 12:02 AM   #4
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Default Re: Best paint for painting over rust

Paint directly over rust is not going to stop the progressive damage of rust, but will hide it from view like an ostrich hides his head in the sand. If the rust is not removed completely, you must convert it to iron oxide before painting. There are several excellent products to do just that, one of which being Rustmort. This is a watery clear liquid, best if applied by brush after removal of flaky rust. As it dries overnight, the rust will turn black, signaling readiness to receive paint without further preparation. It leaves no brush marks and is not a coating, but rather, is absorbed into the rust in a chemical reaction. Wear a full face mask and rubber gloves for safety, but in my case, I was sloppy and even then did not experience any issues from splashing it on my arms and neck.
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Old 01-04-2021, 12:15 AM   #5
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Default Re: Best paint for painting over rust

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Originally Posted by Tim Ayers View Post
While I have the body off replacing some rivets, I thought I just want to protect it from that horrible snow melting brine they put down in the tai-state area.
.
The only way to protect a vehicle from the salt brine in winter is to not drive it. That salt spray gets in everywhere and will rust.
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Old 01-04-2021, 12:19 AM   #6
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Default Re: Best paint for painting over rust

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For me it's always been rustoleum rusty metal primer with a brush. But as stated, you gotta remove every bit of the rust you can. I lived in New England for 7 years and I still have PTSD about the horrors of salt and what it did to my older vehicles. Neil Young was absolutely correct when he said "Rust never sleeps", and I would drive a beater subaru or most anything else besides my early ford in that brine. Just my .02
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Old 01-04-2021, 12:21 AM   #7
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Default Re: Best paint for painting over rust

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The only way to protect a vehicle from the salt brine in winter is to not drive it. That salt spray gets in everywhere and will rust.
We're on the same wave length!
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Old 01-04-2021, 01:01 AM   #8
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Default Re: Best paint for painting over rust

Rust Mort is a great way to convert Iron Oxide into black Iron phosphate which stops it. Then paint over it with whatever you want. Of course wire brush or scrape any loose rust off before the Rust Mort.
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Old 01-04-2021, 02:06 AM   #9
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Default Re: Best paint for painting over rust

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Rust Mort is a great way to convert Iron Oxide into black Iron phosphate which stops it. Then paint over it with whatever you want. Of course wire brush or scrape any loose rust off before the Rust Mort.

Rust Mort is an acidic compound that converts existing rust to an insoluble black coating prior to applying body filler, primer or top coat.



Features
  • Completely removes light rust
  • Converts heavy rust into a stable, workable substrate
  • Creates ideal surface for filler or primer
  • Easy to use
  • Ready to apply
  • Requires minimal surface preparation
https://www.hunker.com/12002764/rust-mort-directions


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Old 01-04-2021, 02:51 AM   #10
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Default Re: Best paint for painting over rust

I use Ospho.. (osphoric acid). I get it at a marine supply place down at waterfront. It sounds similar to the product above....... Mark
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Old 01-04-2021, 06:37 AM   #11
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Default Re: Best paint for painting over rust

Thanks, all. Yes, I have no intention of driving it during winter weather, but that crap sticks around for a long time. Even after a few rain showers you can see residue still on the street.
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Old 01-04-2021, 10:18 AM   #12
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Default Re: Best paint for painting over rust

I have used SEM Rust Shield with the catalyst over the years, and it has stood up to many winters of driving a Jeep here in the Northeast. I have used it on the '40 frame, and trunk floor. I have also used their dual mix structural adhesive, and self etching primers SEM has excellent tech support, call Dave at 800 831 1122 and run your particular scenario by him for his perspective. SEM is in NC.
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Old 01-04-2021, 10:29 AM   #13
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Default Re: Best paint for painting over rust

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The only way to protect a vehicle from the salt brine in winter is to not drive it. That salt spray gets in everywhere and will rust.
You are indeed correct, there is no total protection. The salts gies in places that your eyesight doesn’t and lays there and corrodes.
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Old 01-04-2021, 11:02 AM   #14
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Default Re: Best paint for painting over rust

You don't need to buy expensive rip off rust treatments. The active ingredient is phosphoric acid. Just buy a gallon of the acid, dilute it yourself with water and you will do much better at less than half the cost. Always pour acid into water, not the other way around.
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Old 01-04-2021, 11:36 AM   #15
Tim Ayers
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Default Re: Best paint for painting over rust

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You don't need to buy expensive rip off rust treatments. The active ingredient is phosphoric acid. Just buy a gallon of the acid, dilute it yourself with water and you will do much better at less than half the cost. Always pour acid into water, not the other way around.
Thank you. Curious on a starting ratio you've found to be effective?
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Old 01-04-2021, 12:00 PM   #16
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Default Re: Best paint for painting over rust

I have used Rust Shield from SEM and it's worked very well.
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Old 01-04-2021, 07:02 PM   #17
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Default Re: Best paint for painting over rust

Phosphoric conversion is good. Etching primer has the acid in the primer to etch its way into the metal. Por-15 has an etch formula in it as well. When the surface coating breaks down at some point then the metal will again start to oxidize but a little prevention goes a long way toward longevity.
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Old 01-04-2021, 07:11 PM   #18
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Default Re: Best paint for painting over rust

Paint over rust? WHAT?
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Old 01-04-2021, 09:25 PM   #19
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Default Re: Best paint for painting over rust

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Paint over rust? WHAT?
I wondered if I was the only person thinking that.


Then again, if you start with this you just don't worry so much...
This is a friend's car which is a lot of fun to run around the back roads. The chassis is much better condition than the body.
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Old 01-04-2021, 10:19 PM   #20
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Default Re: Best paint for painting over rust

Let me be the first to agree it must be a lot of fun on the back roads. I tend to obsess about rust the way some people do about bondo. Of course a vehicle with some 1/2" bondo here and there can be a lot of fun too if you can't spring for a new brookville body. I skip the bondo for the most part, but don't come around the Mt Pickett complex with a magnet. For me, it's all about having some fun with old fords, making them run and drive and stop. Driving them some more and then maybe picking up some nice parts or even a new project. I have fairly low expectations, so I am seldom dissapointed.
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