Need help painting plastic bumper.
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Guys,
I have a questions and getting poor adhesion when it comes to painting the bumper moldings which have that texture to it. These are the bumper moldings that go on the chevy trucks which come unpainted and other parts as the rear step pads.
Well, I have a customer who wants to get them color matched. So, I prepped, cleaned and sprayed the plastic adhesion promoter. Next, I layed the primer down and after a couple of hours the primer lifted only on the edge part of the bumper not on the face or smooth parts. What do you guys think is going on? I’ve done quite a few of these already and those turn out great. Maybe my plastic adhesion promoter is bad.
I’m using all dupont line if that helps. Plastic adhesion promotor is aerosol.
Thanks.
What is your prepping procedure? Also if you got a plastic code off of the moldings (usually somewhere on the back), that might be of some use.
Another thing that comes to mind are flash times from adhesion promoter to primer. Pre-baking your parts and using a plastic cleaner on them (while warm)can help you remove mold release agents on stubborn plastics.
are these moulding pre primed??? if so ya shouldnt be putting any adhesion promoter on em especially over gms primer unless ya wash it all off witch my antistat in my system seems ta be pretty good at:blush: if they are raw plastic then i would use the promoter but never on preprimed stuff cuz it will attack the primer thats already on it an that sux;)
I usually scuf em up with a scotch pad first then spray the adhesion promoter. likely if its lifting on the edges only they weren’t cleaned properly. make sure you clean the edges and onto the underside good
[b]jimmo wrote:[/b]
[quote]What is your prepping procedure? Also if you got a plastic code off of the moldings (usually somewhere on the back), that might be of some use.Another thing that comes to mind are flash times from adhesion promoter to primer. Pre-baking your parts and using a plastic cleaner on them (while warm)can help you remove mold release agents on stubborn plastics.[/quote]
Prepping procedure as follows:
clean entire bumper with soap and water.
sand entire bumper with red scotch brite
spray promoter
spray primer
Ding, will I shoudln’t say edges but where the bumper bends and folds is where the primer tends to lift. Will I’m resanding the primer and will keep you guys updated.
Note: The bumper was painted two months ago. Since then it looked great but until now the problem has occured. I’ll try to attach some pics later on tmw.
Thanks guys
I would maybe suggest to use a sanding paste with your pad, it will clean the plastic further. Plastics are more dependent on chemical adhesion thats obtained through cleanliness. I hope your using a plastic cleaner, I don’t see one listed but that will make a big difference, don’t use regular cleaners. Usually the textured pieces are made from some of the toughest to paint plastics so you really need to follow procedure.
I don’t know what duponts exact system for plastics is, I know basf has about a 10 step process to ensure your paint will stick to any plastics…(except PP)
Here it is:
Clean with soap & water
Clean/Scuff with grey pad and sanding paste
Clean with 902 (plastic wash)
Bake for 10 min @ 140
Clean with 902 again while warm
scuff with grey pad
Clean with 902 (i know,, again!)
Apply adhesion promoter ->paint/primerIts a long procedure and I don’t usually follow it exactly unless I know I have a difficult plastic, usually the textured plastics fall into the difficult category. If you don’t have a bake booth then you can only do what you can, I’d suggest you check out Duponts recommendations and follow it precisely.
As I’m typing this I am currently waiting for my adhesion promoter to flash. I’m painting the textured bottom of some GM bumper, I don’t even remember what kind …equinox maybe.. I’m too lazy to go look….anyway earlier in the day when I had some energy I followed those steps and am fairly confident I won’t see this thing again,,,,whatever it is. I guess time will tell. I haven’t had any problems with ones we’ve done before…so far :laugh:
are you saying you painted it 2 months ago and it is lifting now?
I painted all the texture peices on my 03 silverado. I scuffed with a grey scuff pad then used sem adhesion promoter and primed with sem flexable primer surfacer. sanded and painted. 4 years later the only problem i had was on the lower valance where I ran it into a rock.[b]ding wrote:[/b]
[quote]are you saying you painted it 2 months ago and it is lifting now?
I painted all the texture peices on my 03 silverado. I scuffed with a grey scuff pad then used sem adhesion promoter and primed with sem flexable primer surfacer. sanded and painted. 4 years later the only problem i had was on the lower valance where I ran it into a rock.[/quote]Yes, I painted it around 2 months ago.
SEM, makes excellent product and I was never confident in the dupont promoter. I’m going to order the SEM next time.
Jimmo,
Thanks for the info.
I have also found SEM to be a really good plastic system
are you sure the primer just started lifting off or did they bump something. it could also be that you trapped some solvents or to much ap ended up on those corners. with ap more is not better. tough to say without actually being able to see the problem
The sem primer is a 1k product but I used it to fill all the textured plastic on my truck and it never shrank. It just really is a bear to sand.Glasurit 934-70 is a light grey 2K primer and/or sealer that requires no adhesion promoter before it is applied. It works great on all bumpers.
The bumper is cleaned with both waterbase cleaner and solvent base cleaner before sanding(to remove mold release waxes and to remove any shipping primers that can cause adhesion problems). It is then sanded properly, and then recleaned. Apply the 934-70 per the directions. If used as a sealer, base and clearcoat with flex. Hardener in the base always helps on adhesion-especially on solid colors.
I have used this on several raw and textured bumpers and have had great success with it.
I’ll second that, I switched from RM 865 to 934-70 direct to plastic sealer & am very happy with it.
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