Pro tip: that 'good enough' primer job will come back to haunt you

Had a customer bring back a 2020 F-150 we painted last fall, and the clear was already peeling on the hood. We rushed the primer sanding to 180 grit to get it out the door. Now we're redoing the whole panel on our dime. Anyone else get burned by skipping a step to 320?

3 comments

3 Comments

john4302mo agoTop Commenter

Our shop manager in Toledo always said primer needs a mechanical tooth, not just a scratch pattern. Sanding to 180 leaves deep grooves that hold air and moisture. That trapped solvent eventually pushes up against the clear from below. It looks fine for a few months, then it just lets go. We switched to a three step primer sand years ago, 180, 320, then 500 before base. Never had a comeback for peeling after that.

nathan_barnes2mo agoMost Upvoted

Yeah, that tracks with what the old-timer at the local supply house told me. He called 180 grit scratches "little ditches" that never really seal up. Said you can watch the solvent boil out of them if you spray too wet. The step up to 500 before color makes total sense, even if it feels like overkill at the time. It's one of those things you only learn after seeing a job fail.

dylan41312d ago

So does that three-step process add much time per panel? I'm starting to think one more pass on the primer is way cheaper than explaining to a customer why their paint looks like a snake shed a year later. The solvent boiling out of those deep 180 scratches makes sense, I've seen it happen on test panels where it looks like little pinholes after the clear flashes. If 320 and 500 takes an extra 15 minutes but saves you a whole repaint down the road, that's probably a no-brainer.