Hi guys. I am repainting my bumper cover which is plastic or urethane (bmw).

I sanded the pits and scratches then used some filler primer, sanded, and then regular primer, about 3 coats and sanded at 600 grit. I may have sanded it a bit finer here which i think might be a problem.

I sprayed the base coat (from automotivetouchup.com) about 3 coats and it looked great.

I finished my clear coats last night around 8 PM. Again about 3.

Today i mounted the bumper at around 4:00pm and my finger nail scratched the paint right off. I'm not sure if maybe its because the clear is not fully dry or the paint is not adhering to the primer. This is a real bummer since the whole process took weeks.

Is there anything i can do at this loint or does it need to be redone?

Rezilient wrote:Hi guys. I am repainting my bumper cover which is plastic or urethane (bmw).

I sanded the pits and scratches then used some filler primer, sanded, and then regular primer, about 3 coats and sanded at 600 grit. I may have sanded it a bit finer here which i think might be a problem.

I sprayed the base coat (from automotivetouchup.com) about 3 coats and it looked great.

I finished my clear coats last night around 8 PM. Again about 3.

Today i mounted the bumper at around 4:00pm and my finger nail scratched the paint right off. I'm not sure if maybe its because the clear is not fully dry or the paint is not adhering to the primer. This is a real bummer since the whole process took weeks.

Is there anything i can do at this loint or does it need to be redone?

I don't know what you should do now, but did you use adhesion promoter on the plastic? I've been considering spraying the black plastic trim and molding on my Tundra to match the paint on the body. Adhesion promoter was recommended by the paint guys.

Yep, good point, in fact i did use adhesion promoter before the primer.

Are these all 1k style aerosol products by any chance????

DarrelK wrote:Are these all 1k style aerosol products by any chance????

Everything was from automotivetouchup.com. Their lroducts came highly recommended but in hindsight i should have used an air gun.

Anyway at this point i have the job done with some obvious parts where not enough clear that needs to be touched up, and some minor imperfections that i plan to wet sand at 1500-2000 grit and also reclear. I guess the question what might be causing the paint to come off so easily, possibly not enough clear?

When the paint "scratches" off does it flake or does it seem soft underneath?

My guess is that your filler/primer and primer layers were not fully dried when you put the topcoats on so you've sealed them in. If all your products were acrylic lacquer based this will just take time but you do run the risk of delamination as the thinners from the primers try to escape, but can't because the top layers are now hard, so push the paint off in bubbles.

IK filler primer takes a long time to dry, 24 hours or more and you cannot rush it. Same thing with any subsequent coats - they must be light coats and allowed to flash off properly so that they will not over soften when the next coat is applied.

NFT5 wrote:When the paint "scratches" off does it flake or does it seem soft underneath?

My guess is that your filler/primer and primer layers were not fully dried when you put the topcoats on so you've sealed them in. If all your products were acrylic lacquer based this will just take time but you do run the risk of delamination as the thinners from the primers try to escape, but can't because the top layers are now hard, so push the paint off in bubbles.

IK filler primer takes a long time to dry, 24 hours or more and you cannot rush it. Same thing with any subsequent coats - they must be light coats and allowed to flash off properly so that they will not over soften when the next coat is applied.

The paint seemed soft underneath, not flaking.

I think the clear might not have been fully dry and maybe the chemicals softened the base layer (does that happen?) so it was all too easy to peel. However the base and primer were done the week previous so I think those coats would have been fully cured.

About fixing the job - for rough areas am I right in my approach: 1) sanding the rough/damaged spots at 1500 grit, 2) buffing with an orbital and compound, 3) then clear those areas again?

Thanks.

Acrylic paints are only about 20% solids so that's a lot of thinners you're putting on if applying too thick. Let it all completely dry then take any rough areas down with P1200-1500 (some will say you can go coarser) on a block and reclear. No need to buff. Light coats! The thinners will soften and melt in to the layers underneath so you'll get a good bond.