Paint over rust, or remove the rust?
Posting Guru
Joined: Mar 2002
Posts: 2,070
Likes: 2
From: Boise, Idaho
Paint over rust, or remove the rust?
Hi all,
In the last few years, I've had a change of philosophy regarding rust. Used to be that I wanted it completely gone. Must be a result of living in the Northeast where rust attacks cars with a vengance.
Removing rust is not trivial. I've heard of people completely dipping car bodies into acid to get the rust off. Then I heard that the acid got into the seams and later erupted from beneath the paint that was painted over the seams.
Sandblasting rust off of metal is pretty harsh and it exposes bare metal where before it had been under the original oxide coating or paint (or both). Unless you are pretty fastidious about getting the metal cleaned off, prepped, and refinished, you could be asking for trouble later.
My current theory for treating rust in places like frames, under running boards, and under the body is to knock the top layer of rust off, wipe the metal clean with lacquer thinner, then paint POR over it. Later repaint with chassis black, or whatever is suitable. This method does not disturb any existing oxide or paint, is less work, and may be a longer lasting coating.
What are other people doing in this situation?
Post Fiend
Joined: Apr 2002
Posts: 7,157
Likes: 1
From: Central Kali
Paint over rust, or remove the rust?
I made a fence with used pipe that was pretty rusty. I power brushed the loose rust off. Primed and brushed industrial enamel on fairly thick. Looks good after several years.
Senior User
Joined: Jul 2001
Posts: 311
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From: Walla Walla USA
Paint over rust, or remove the rust?
Paul...I agree with you. It is nice to end up with a nice smooth frame or other part although I don't know if it is worth the trouble. By taking a wire brush to a drill and getting as much off as possible...cleaning it up and then doing the POR...I think it is in good shape. Nothing is going to get through POR.....
The finish might not be as factory smooth but in the long run....does anyone really look and compare?
Now on doors, pickup bed sides etc.... sandblasting is an easy quick way to get rid of the paint that needs to go in the first place. What do you think?
The finish might not be as factory smooth but in the long run....does anyone really look and compare?
Now on doors, pickup bed sides etc.... sandblasting is an easy quick way to get rid of the paint that needs to go in the first place. What do you think?
Posting Guru
Joined: Mar 2002
Posts: 2,070
Likes: 2
From: Boise, Idaho
Paint over rust, or remove the rust?
JML,
Where it can be easily seen, fenders and such, I agree that the finish should be as smooth as is practical. But on frame members, driveshafts, rear axles, I say POR and chassis black it the way to go. Not just because the cosmetics don't matter as much, but also because the process of sandblasting these functional parts could cause them to be compromised; exposing the bare metal could lead to eventual rusting and/or contamination with blasting media.
Senior User
Joined: Jul 2001
Posts: 311
Likes: 0
From: Walla Walla USA
Paint over rust, or remove the rust?
[updated:LAST EDITED ON 13-Aug-02 AT 11:48 PM (EST)]Paul, yeah your're right. I would leave those parts alone as well. Clean em up and paint em chasis black. Thanks jim
Post Fiend
Joined: Jun 2002
Posts: 13,873
Likes: 3
From: Atlanta GA
Paint over rust, or remove the rust?
Having a bit experience with tractors (big rigs) painted with Mar-hyde, what happens is you cover up the rust, but, over time the steel rusts away in layers the way it was rolled and you end up with a good looking part that is basically rusted through and weak. I think removing the rust as much as possible and then a layer of POR-15 is the best way to go.
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