Body restoration question

[Gil]

This is a question about replacing old rusted metal and how to prime the metal. Let's say, for example, you are replacing part of the rear wheel wells because the shock tower area is rusted out.

Obviously you would take the donor (or new pieces) of sheet metal and clean them down to bare metal (acid dip or bead blast). Then you would completely prime the pieces with weld-through (zinc-rich) type primer? I was thinking that painting the entire shock tower/spring perch with zinc-based primer would extend the life of the metal in this area of the car?

But for the existing adjacent good metal in the wheel well, how do you prep. the metal? I would think that you clean some of the adjacent metal to bare metal so that you can weld to it and prime paint it. After that, what do you do? You can't keep removing old paint and undercoating (and maybe light surface rust) to get to clean metal otherwise you'd end up doing most of the car?! Should you prime a small adjoining area only of the existing metal with weld-through primer? Then, prime the remaining bare metal with epoxy primer?

In other words, is there a primer that is compatible with zinc-rich primer and existing paint and maybe even a little rust? And then you would use epoxy primer over the base primer?

Basically, because a wheel well is exposed to moisture and dirt, it needs to be really well primed and painted and undercoated to maximize the life of the repair.

Also, would it help to drill out the spot welds for the spring perch, clean the mating surfaces to bare metal, prime with weld-through primer, and then weld back up? (This would be done on the bench.)

TIA,

Gil

73 02

[Guest Anonymous]

Single part zinc or any other single part primer is not going to be up to the same long term protection and bond you will get with a 2 part automotive primer, like a good epoxy.

Best scenario for me would be to forget the weld thru, prime with a good epoxy, clean away epoxy as needed to weld as you need to.

BTW - the weld thru burns away just like any other paint I have come across

David

[Gil]

So weld-through primer burns away?? Then it's not much good is it? It sounds like priming everything with epoxy primer first is bets and then clean away waht you need to weld...

Gil

[esty]

So weld-through primer burns away?? Then it's not much good is it? It sounds like priming everything with epoxy primer first is bets and then clean away waht you need to weld...

Gil

weld it....sand or grind it smooth then use a 2k epoxy primer over that....it's the best protection against future rust you can buy

you can mix it and spray it with a PreVail bottle sprayer

[Gil]

the correct thing to do with two mating surfaces is to spray them with weld-through primer before you weld? I can see what you mean by smoothing/grinding exposed surfaces, but I thought that the purpose of the weld-through primer is to help protect concealed bare surfaces? I don't think you should create unprotected surfaces where moisture can get in and be trapped.

Gil