rust preventative vs epoxy primer (1 Viewer)

[troy scott]

i have a question about primers or base coat rust preventative. im not a auto body man or painter ive hired a painter. He has primed all my parts in a zinc base primer that we agreed to a few years ago. Fast forward to now, i have him working on the tub he has done the body work and its prime time. he doesn't want to use the zinc primer he says its thick and clogs stuff up his words were "im not a fan" he says an epoxy primer over clean metal is all i need. on anything else i would agree, but the curse of the fj40 rust scares me to death. Ive been working on this project for a decade i don't want to ever have to do this again. whats your opinion should i insist on the zinc or am i being paranoid. He is the body man and a good friend of mine, and has been with me since the start of this project. He is right that stuff is nasty thick and kinda tough to sand. I wish i had the name of it but i don't have that with me. The tub is media blasted and clean. whats your opinion should i insist on the zinc or am i being paranoid.

Thank you for your time taken to respond!

 

[Splangy]

I don’t think anybody here can recommend the zinc without knowing what product it is.

That said, it’s probably not doing much besides adding to the film thickness of your paint system. You’re not going to beat an epoxy in terms of adhesion and the zinc isn’t going to do anything unless your paint is chipped and exposes the steel/zinc to moisture.

The only place on the body I would consider using a zinc paint is on the bottom of the tub/fenders.

You mentioned that the body work is done. Does that mean the body filler has been applied and blocked? The zinc needs to be in contact with the steel for it to provide protection. It won’t do anything if applied over bodywork.

 

[troy scott]

by done with body work i ment done welding in patches and my new rear quarters i guess thats far from done LOL no mud work yet if the zinc is a good idea on the bottom and under the fenders why not the whole tub for added protection not the dash i understand that but i had more rust on the top of my floor than the bottom

 

[Splangy]

The floors might also be suitable if you’re expecting to scratch them up. Again, the zinc doesn’t do anything besides add to the thickness of the paint system, drain your wallet, and make your paint guy’s life miserable if the steel doesn’t see moisture from the environment. I assume you don’t plan on scratching the rest of the body up to bare steel.

 

[troy scott]

ok thank you for your time

 

[PAToyota]

From working with architectural (building) products, the zinc paint is a toss-up. It definitely isn't the same as galvanizing something. I'd tend to agree with Splangy that a good epoxy primer is going to do a better job of sealing things up and be neater than the zinc paint on bodywork. If you're concerned about the underside, use a spray bedliner on the underside to give it more abrasion resistance.

Floorboards are likely rusty from water getting in and then sitting there. Carpet or padding can be horrible for that. They act like a sponge and just hold the water there against the metal instead of allowing it to evaporate. That's why a lot of people with open-top or removable top vehicles will use a bedliner on the interior as well.

 

[troy scott]

thank you for your reply i am also putting bed liner top and bottom i am convinced that the epoxy is the way to go

 

[RUSH55]

Talked to the my local paint supplier about these primers. I’ve been using the zinc weld-thru primer on repair work I’ve been doing, and spraying the insides of areas that are being closed in. My plan was to do spot repair with the zinc primer, then once done, spray everything with epoxy primer. The paint guy said the epoxy and zinc are not compatible, and suggested just spraying primer sealer over the zinc, and epoxy over everything else, then sealer again, then laying paint over that.

 

[Prairie Swamp]

Not a coatings expert but it's my understanding there are only a couple chemistries that are totally impervious to water including water vapor. Epoxy is one of them. Epoxy all the way unless you're talking POR15 which I've done on appearance items as the first coat. But that's a whole other can of worms and this place def has POR15 haters.

 

[Splangy]

Not a coatings expert but it's my understanding there are only a couple chemistries that are totally impervious to water including water vapor. Epoxy is one of them. Epoxy all the way unless you're talking POR15 which I've done on appearance items as the first coat. But that's a whole other can of worms and this place def has POR15 haters.

All coatings, including epoxy, are permeable to small molecules such as water vapor. Some (although not typical in automotive coatings) will have a published water vapor transmission rate. Most epoxies have a relatively small transmission rate compared to other coatings. They also excel in their superior adhesion to a properly prepared substrate compared to other coatings.