Can I pant over surface rust?

Question

My hubby and friend are fixing up an old mustang. They wanted me to ask this...
If they ground down some surface rust and found that there was still some rust underneath that, if they bondo it up and then paint over it, would it last? I said no cuz they're just painting over bad metal but I figure I'd ask anyway.

Answer 1

You can paint over your surface rust if you use a coating like KBS RustSeal. It's a moisture cured urethane that's formulated to seep deep down into all the rusted metal pores and block all access to moisture & oxygen. RustSeal is a non porous coating that's even strengthened with any exposure to moisture. You apply it directly to the bare rusted metal that's been cleaned & wirebrushed to remove flakiness...brush marks flow out great & cures rock hard. Your rust will not return. It's similar to POR but RustSeal has better adhesion and finishes. Satin black looks like OEM.

Answer 2

Well this depends.. If the metal has not rusted all the way through the metal, then they should be able to grind down the rust, clean the area, and bondo it up and paint over it... and it should last. If the Metal is rusted all the way through then they will have too Cut that part out and weld on New Metal.. Bondo lasts long and should do the trick.

Answer 3

You're absolutely right. I tried the same thing on a Dodge Dart and also applied a chemical that allegedly neutralized rust. It really didn't work. The paint started to bubble up in a year or so.

They call rust "cancer" for a reason. It spreads, and the only good way to deal with it is to remove it all.

You have only two alternatives here: Keep on grinding until the rust is all gone, even if this means you grind a hole in the metal. Or break out the Sawzall and cut out the rusted metal entirely. Then replace the rusted area with either some welded-in new metal or a fiberglass patch.

Answer 4

There are phosphating compounds that convert rust into iron phosphates. These are used in some primers to go over surface rust. There are also paints using special oil bases like fish oil (rustoleum paints) but honestly it is better to sandblast the rust holes out because it will just continue rusting under most paints and just fail under the bondo. You are right. My friends run body shops and love the small sand blasters.

Answer 5

Sure they CAN, but if you leave any rust whatsoever it will just rust out again. Eliminate all rust. If it leaves holes, fiberglass over the holes on the back and bondo on the front, or, in the case of a fender which is removable, take it off and replace it. Tell them from now on to listen to you, oklatom said so.

Answer 6

There's primer that stops rust, but if they bondo over the rust, the primer wouldn't be able to reach it. And if they primer it first, the bondo won't stick. They need to get all the rust out.

Answer 7

nope..no good
remove rust refill with either lead solder or fiber glass, and then use bondo after that the primer sanding and the paint.
is not a waste of time and money a properly done works pay back.always pay back.

Answer 8

This repair will fail if all the rust is not removed.After removing rust, use a self etching primer as a base before using any filler

Answer 9

Only if they use a primer that is specifically designed to cover directly over rust. POR15 paints are supposed to be very good for this.

Answer 10

No! Never leave rust... it will eventually eat through. Sand the rust off first.