Can I use Bondo over Ospho?

[MarkG]

I just welded in some new metal rust repair panals, ground them down, and Ospho'd them. The Ospho directions say you can paint over it, but the directions on the Bondo can say 'sand down to bare metal'!

If I sand down to bare metal, as Bondo says, it seems like I'll be losing the benefit of treating my repair panals with Ospho in the first place! Whose directions do I follow? Bondo's or Ospho's?

Thanks!

[astroracer]

Clean off the Ospho. The plastic will have issues bonding to the coating. It's better to have "plastic to metal" adhesion to reduce de-lamination issues down the road.
In all actuality, if the metal is clean and rust free, the Metal Prep really isn't doing anything that a good epoxy primer wouldn't do once you get to the paint stage.
Mark