Hi All,

First post in a looong time but my last paint job, almost 10 years ago, came out fantastic thanks to help from this forum. Now onto the next project.

I used SEM etch primer (rattle can) on my floor pans. I want to use the 3M rattle can undercoater, but wonder if I need to seal it with a primer/sealer before I apply the undercoater. The SEM tech pages say not use it under color, but not sure if the undercoater would be considered a color coat.

Also, whether I primer/sealer or go direct with the undercoater, I'm assuming I need to scuff the etch prime. It's got a glossy sheen to it right now, and was done 2 days ago.

More back history. Car is a '71 240Z, currently on a rotisserie. I removed the original tar undercoat and paint down to bare metal. Ground out all surface rust with a wire wheel. Welded in patches where rusted through. Used rust converter (Eastwood) on areas where surface rust had been or areas that I couldn't get into very well. Then spot primed with Eastwood Rust Encapsulator, followed by the SEM etch primer on all areas.

Still have the back half of the car to do, as well as the front fender wells and engine bay. All of this will get the undercoater except the engine bay. Considering switching to epoxy, but the question would still be same of whether it needs another primer on top before undercoater.

Thanks in advance for sharing your wisdom. JoeK

That 3M undercoat seems to stick to anything -- but probably a good idea to contact SEM tech support to make sure.