Refinishing plastic bumper

Anything goes in the world of fiberglass and plastic



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PostPosted: Sun Jan 10, 2021 4:41 pm
Hello:

I'm new to this process and have watched a lot of YouTube videos to get me going. Avid, good, detailer, I'm never really taken on resurfacing a bumper. I purchased my daughter a 16 year old Honda Accord. The bumpers need to be refinished. I'm working on the rear now and here is what's going on:

It's been sprayed at least once before, from OEM. They didn't do a very good job as the color is off and the clear was chipping/peeling. There are also two small areas where a chunk was taken out. I removed the bumper from the car and started on the spots that needed to be filled. I used 100 grit and a random orbital palm air sander and got these areas cleaned up. I used this product to fill them:

https://www.amazon.com/gp/product/B0046 ... UTF8&psc=1

I admit, I'm not impressed with it. It said to wait 30min., I waited an hour. It was difficult to sand and I still don't have it smooth, despite dropping down to 80 grit for those areas.
It actually started to gum up even after I moved to hand sanding. A bit frustrated, I shifted to running 240, with the air palm random orbital sander, over the rest of the bumper. I feel like I got it to a spot where the rest of the bumper is smooth and could take primer, except for the repair areas where I used that product. There? I am disappointed to admit that I went through all the clear, paint and am down into the material of the bumper in several areas. This, in an effort to get that product smoothed out.

Before I did more damage, I stopped and walked away from it and decided to seek guidance here. I obviously need to smooth those areas out. Given I'm now down into the material of the bumper, how do I build the sanding up to 240 where I can apply primer? It seems like I need to get everything even and start laying down some high build primer so those spots even out. Also, should I apply the adhesion promoter before the primer? Do I apply the AP to just the areas down to the material of the bumper, or over the entire bumper? I have a bulldog product I purchased that I planned to use. What's a good high build primer to use for this application?

My original plan was to get those spots repaired and get it evenly sanded to 240. Spray down the adhesion promoter and then high build primer x2-3 coats. Work the sanding up to 320/400(wet)/600(wet) and then lay down the basecoat, which is a metallic. From there, I have 2k clear.

https://www.amazon.com/gp/product/B00W2 ... UTF8&psc=1

I'm using https://www.automotivetouchup.com/ rattle cans, FYI, for the base.

Can someone get me back on track, please? Photos are in the link below. Thank you!

https://link.shutterfly.com/dl4OfrhAWcb

Shumax

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PostPosted: Mon Jan 11, 2021 8:32 am
If only Youtube could be held accountable for some of the rubbish that's posted on there.

You'll struggle to get that repair area smooth just by sanding further down. So.............go up.

Mix up some everyday car body filler and apply a thin coat to the whole area. You can also use it to fill the scratches and gouges all over that bar. See if you can actually get the body lines straight.

Sand with P180 on a block. Don't sand it all off - just get it smooth and flat. You may need to repeat for any problem or low spots. Sand again with P180 and finish with P240 on your DA.

Prime, base and clear. Did you remember to get the right kind of mask? That clear contains isocyanites which have this nasty habit of killing people.
Chris



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PostPosted: Mon Jan 11, 2021 10:32 am
Thank you for the reply. Yes, certainly do have the mask. I read that's some nasty stuff - wow.

So, I went out today and found some body filler for plastic bumpers. I sanded the bumper from what I had used and then hit it with the adhesion promoter. It's currently drying now. I plan to then apply this filler almost like a skim coat in those areas. From there, I will do as you suggest - sand it smooth and then prime and take it up from there.

Thanks for the input - it's appreciated!
Shumax

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