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BUMPER PREP

#1
I normally don't do collision work and the few times I have replaced bumper covers they came primed. I have a Yang Tong after market raw bumper with no painting notes or even what material it is. How is the best way to prep this. I was thinking wash with tide powder detergent and a gray scotch pad. Wash with dawn. Wash with waterborne wax and grease and either epoxy prime or epoxy seal and paint? Do I need an adhesion promoter ? I have Bull Dog In a spray can. Please help me if you can. TIA.
 

Chris_Hamilton

Trying to be the best me, I can be
#2
Hey Sarge, start by making sure there is no primer on it. Sand a little and see if it is raw or primed. Most Tong Yang stuff comes with a waterbourne primer on it. If it is primed you can scuff it with a gray scotchbrite pad and Dawn or Ajax (I guess the TIde would work as well), I use Presta Scuf Stuff. If it is raw (it'll have a slight sheen to it if raw) do the same procedure. Keep the pad pressure light in either case. Rinse, dry, and when ready to shoot wipe it down with a water based degreaser like SPI 700. If it's raw you need adhesion promoter, if it's primed you don't.
Word of warning the adhesion promoter in the spray cans is really hard to put on nice and even. Much better to use the stuff that you can spray out of your gun irregardless of the brand. I use my base or sealer gun when spraying it. You can put the leftover back in the can when done as well.
 
#3
Hey Sarge, start by making sure there is no primer on it. Sand a little and see if it is raw or primed. Most Tong Yang stuff comes with a waterbourne primer on it. If it is primed you can scuff it with a gray scotchbrite pad and Dawn or Ajax (I guess the TIde would work as well), I use Presta Scuf Stuff. If it is raw (it'll have a slight sheen to it if raw) do the same procedure. Keep the pad pressure light in either case. Rinse, dry, and when ready to shoot wipe it down with a water based degreaser like SPI 700. If it's raw you need adhesion promoter, if it's primed you don't.
Word of warning the adhesion promoter in the spray cans is really hard to put on nice and even. Much better to use the stuff that you can spray out of your gun irregardless of the brand. I use my base or sealer gun when spraying it. You can put the leftover back in the can when done as well.
This is very glossy and looks raw to me. I am going to get started on it today so I'll see if it is in fact raw ? thanks for your input.
 
#4
Here's how we do raw plastic in my shop:

1: Wash inside and out with strong Dawn soap solution. Wash inside very well because handling can introduce contamination from the back onto the front.
2: Scrub the pee out of the entire exterior with gold pads and plastic prep paste. We have switched to a less abrasive method because the soft plastic when scratched can leave raised scratches that require work later. Some people have good luck with grey pads and Scuff Stuff as Chris specifies.
3. Dry and clean about three times over with SPI #700.
4. Wipe with anti-static wipe (optional).
5. Apply adpro, SPI #600 is a good one.
6. Apply flexible sealer, SPI epoxy mixed 2:2:1 works well
7. Paint.
 

jlcustomz

evil painter
#7
Probably 99% of the average bumpers a paint shop will see these days are either polypropylene, polyethelyne , tpo or teo , which all need special care if not primed. Yellow urethanes or aftermarket duraflex fiberglass composite are just about the only exceptions.
The extra step of washing the backside on something you will unavoidably touch before completion is well worth your time.
Avoiding getting any heavy scratches in these materials is a must. Not only will they too easily show through later, a long scratch you can easily feel with your fingernail on some of these thinner bumpers is a weak spot that could show through later if bumper gets flexed opposite the sides of a deep scratch, kinda like score & snap.
Flame treating with propane torch is the only substitute for adhesion promoter with these types of plastic. What is misunderstood about this method is that the plasma in the flame brings up the surface oils to be wiped off, it isn't heat.
 
#8
Probably 99% of the average bumpers a paint shop will see these days are either polypropylene, polyethelyne , tpo or teo , which all need special care if not primed. Yellow urethanes or aftermarket duraflex fiberglass composite are just about the only exceptions.
The extra step of washing the backside on something you will unavoidably touch before completion is well worth your time.
Avoiding getting any heavy scratches in these materials is a must. Not only will they too easily show through later, a long scratch you can easily feel with your fingernail on some of these thinner bumpers is a weak spot that could show through later if bumper gets flexed opposite the sides of a deep scratch, kinda like score & snap.
Flame treating with propane torch is the only substitute for adhesion promoter with these types of plastic. What is misunderstood about this method is that the plasma in the flame brings up the surface oils to be wiped off, it isn't heat.
Good info. I don't think I have the balls to try the flame Thanks I enjoy your posts. I check the forum every day. I turned 68 today and have been doing this crap for 50 yrs off and on 30 yrs. every day in my own shop. It is hard to stay up to speed on changes. .You guys are the best. No BS on this site
 
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