Question about sanding/coating 2K primer surfacer

M

mrennie

Promoted Users
I have seen on the SPI TDS as well as some training documents from PPG that after block sanding a urethane primer-surfacer, it needs to be coated with something, and not just left in a sanded state for any length of time. Some documents say that if left sanded more than XX number of hours (or days), the primer needs to be scuffed with a scuff pad before applying another product.

I would like to understand why this is required...what happens to the sanded urethane after it sits? Do the sand scratches change or does the primer develop a film preventing adhesion?

I'm going to be doing my block sanding in sections as I don't get as much garage time as I'd like, so I want to figure out the best plan possible to avoid problems or waste of product.

Thanks

Michael
 
Exposed 2k primer/surfacer will easily absorb contaminants and moisture. If you are going to do a panel at a time just be sure to apply a sealer before letting it sit for extended periods of time. I use epoxy primer mixed 1:1:1 in cases like this. Then when ready to paint I wet sand with 600, clean, mask and spray.
 
10-4, thanks for the explanation.

I never thought of needing to mix the epoxy as a sealer....I just got another gallon a few weeks ago but didn't get any reducer :(

Any issues with just spraying a regular coat of epoxy and doing a final block block on that before moving to paint?
 
do all your blocking, let the panels sit as long as you want... when you are ready to paint give all of them a light scuff with a scotchbrite-it takes only minutes, shoot a thin sealer coat of epoxy and then your paint.
 
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