HELP! Did I mess up? Primer/ Body Prep

[67GT500#1594]

Everyone,

I'm trying to get my car to the body shop to get painted. I'm trying to detail the underside and engine compartment before paint and then follow the paint overspray patterns. I washed off the Ospho and dried everything off. I scuffed the underside with 80 grit and used "Rustoleum Professional Primer" to help keep the flash rust from starting. I have a few places I needed to detail out with bondo from drag racing damage. The car immediately started to flash rust pretty good. I was planning on using the SPI epoxy "Red Oxide" as many do. Now I've been told, I messed up, I need to remove all the rattle can primer with lacquer thinner down to bare metal again? I've tried a few areas and this primer has bit in and won't come off!!

How do I fix this? Should I leave the primer on and scuff it like hell and take the chance or?? I didn't expect the Rustoleum Primer to bite in that well but it sure did!!

Regards,
Matt

[rhjanes]

Talk with the body shop you plan on using.  Many won't want to work over something like what you did.  But I'd let them remove it and then let them build it up.  You should have a shop working with you on the correct primers/surfacers and colors.

[Coralsnake]

Pretty much everything in the first photo would have been chassis black without primer underneath  (assuming you are using factory standards)

Then you have the potential issue of paint incompatibility. Most paints today are part of a "system" where all coats are engineered to be compatible.

Having said that, chances are you will be fine.

[cboss70]

Rattle can primer is porous so surface rust can happen underneath- certainly wet sanding it will cause a mess. First step with clean metal is to SEAL it with a two part primer and if you started with spray cans and its sat you may want to consider restriping it and then sealing right away. 

Spray can primer would not be correct but depending on what you are doing it can hold up for many years if surface prep was done right and it was top coated right away to avoid flash rust (because again the primer is porous).

Most modern paint products are made to be used with their other paint/primer products in that family.  Many will work great with other brands but there no guarantee. If that needs to happen try testing things on something that doesn't matter if the paint lifts.  I've seen many people use their favorite primer product and then just use a paint sealer right before the paint coats to ensure good adhesion, it smooths out the base, and seals out all the base materials you used.  Your body shop or a local automotive paint supplier will be able to give you specifics and recommend products that meet your needs.

[Greg]

Matt,

I know it is more work but it is A LOT less money to do it right now than to have the paint release itself in a year or two.  Chances are it will be fine but I wouldn't roll the dice when you have an opportunity now of a sure thing when you do it correctly.

Greg

[67GT500#1594]

Thanks everyone!!

Yeah, it pretty much sucks at this point but like everyone says "better now than later!". I'm letting the body shop do the top, he's said don't mess with it. I was trying to get the underside detailed only. I must have really done a great job prepping because it set up perfect!

I'm gonna get a small sandblaster and hit the bottom side and engine compartment again, start over. Do my detail work and the expiry primer it with the right stuff! Appreciate all the great responses!! 👍👍👍

[JohnHouston]

You are on the right track.  Do it right and you won't regret it.  On the rotisserie it will only take a few hours now. 

John