After fairly extensive repairs, I'm prepping the underside of my cab for por15. To limit material usage, I'm just going to concentrate on the seams and previously rusted areas.

After that, an epoxy primer on the whole area, but I'd like to not sand the por15.

Or would a regular 2k primer be ok since there will not be any bare metal?

The whole area will be prepped with the por15 etching spray. No intentions of sanding any of it. Fyi

Any advice?


Thanks

Not a fan of POR15 it is highly overrated and will eventually crack and allow moisture to get in and rust to form under the surface.

If you can, media blast the rust from the metal. If not, then use a rust converter (Phosphoric Acid) and apply coats until the rust is fully converted. It will turn black.

You will need to neutralize the acid by applying a fresh coat of the converter and while it is still wet, wash with soapy water. The soap will neutralize the remaining acid.

Rinse thoroughly and blow dry with an air hose. Next, clean and prep for Epoxy Primer.
Shot 2-3 coats of epoxy primer allowing each coat to flash per tech sheet.

Test


Well, this forum software leaves a lot to be desired. Typed a big response and get sql error.

Try it this way... always copy a big response before submitting.

You might want to do a search on here for POR15 and see what others have actually experienced.

You asked for advice, I gave you what I know to be true. What you do with it, is entirely up to you.

Well, I'm an advocate for using MCU's, POR-15 included. I've been using it for over 30 years. Never under "good paint", but on floors, undersides of cars, and on the backsides of my welding and patch jobs. I've even used the silver (the better one to use to block rust) as a primer on painting chassis.
I use 2 ways to topcoat MCU. First is to do it when it is just barely tacky, not wet, not dry. The only time paint, or undercoat/bedliner, will stick to it. If I don't have time to do a complete job, I at least put a coat of primer, or one coat of paint on it when it's time, then come bakc a day or 2 later, scuff the primer and put on the rest.
POR actually makes a product called "Tie Coat" that is supposed to give adhesion to POR-15 to paint over it.

Sorry for the ignorance...

Mcu ?

acro wrote:Sorry for the ignorance...

Mcu ?

MCU = Moisture Cured Urethane

They contain crosslinkers that are activated by the
moisture/humidity in the air.