I am planning on bringing my 240z to a shell and then blasting it down to bare metal. I was wondering what to do with underneath the body, inside fender area, and frame rails. I have seen many people that use POR or just undercoating such as gator coating. My question is can you coat the car with POR and then shoot undercoating over it or should you just use one or other other? If you undercoat, do you need to POR the interior or is respraying with paint sufficient? I tried searching, but most just showed restorations just using one or the other.

http://www.classiczcars.com/forums/thread46823.html

I am really curious about what responses you might get to your question. I have used rust bullet (similar to POR 15) and then undercoated over it. I have also experimented with spraying transtar 4423 anti corrosion spray into crevices and then undercoating over that area with the idea that the transtar flows more freely and will flow into cracks better.

I would be curious to see long term how undercoat will stay stuck to POR or any of the moisture cure urethanes. The catalyzing of those product essentially ties up all the chemical bond sites in the film leaving you to go after a scratch pattern for a mechanicall source for adhesion.

I spent years helping develop a single stage 3000hr barrier coat product which solved that issue and number of other short comings the moisture cured urethanes bring to the market. I'm so old and tired they put me to work doing tech support for the product out of my house. Life is good.....

Thanks for the info. I probably don't want to take the risk that the undercoating would start to flake off. I think I am going to just por or rust bullet the metal on the parts that can't be seen. I don't know what to do for the undercarriage and interior though. How well does POR's self etching primer work?

Edited September 10, 201212 yr by nismospek

Bruce,

Is there any info on the 3000hr barrier coat you mentioned? Was it tested with a salt spray or anything like that?

Mike

You bet. We tweaked and tested and tweaked some more until we got B117 salt spray numbers to 3000 hours and that point figured there wasn't much to be gained by going further. I remember Mike Ditka waiving 500 hour panels of the R product on one of their ad campaigns and just smiling.

Shoot me a PM and I'll find you a dealer.... I know we have 'em in Idaho 'cause I set most of them up.

Can you throw undercoating over the Tie Coat primer? I would really like the undercarriage to be black.

Got an email from the POR and they said that it should be okay to put rubberized undercoating over POR as long as you scuff up the area. They also said their was no need to throw primer on it.

Not a very scientific test as the data became useless when they put the plate in a pool and on a roof but interesting:

Rust Bullet Prepped seems to be the way to go.

http://www.thesamba.com/vw/forum/viewtopic.php?t=131753

Edited September 13, 201212 yr by Blue

This one is more interesting... keep Por out of the sun and it works nicely:

http://www.drjing.com/Mini/BLOG/SideBySide.htm

Pretty cool stuff. I think I am going to rubberize the undercarriage and POR the interior then cover it with the self etching primer and paint to match. Would it matter which side is PORd?