What primers are you using on urethane bumpers for good adhesion. I used some polyvance Flex Filler 2 to smooth the front bumper as best I could but need a little advice on primer.???? Epoxy- urethane - primer filler - adhesion promoter - flex additive.
Thanks, Bubbagum

 

Important question: What are you specifically painting? Is it raw urethane? Or is there a coat of primer or sealer ....over the urethane now. Small section or whole new bumper. Hard to give specific recommendions w/o knowing what you're doing.

Raw Urethane or Bumper/plastic item:
Generally on a bumper cover or urethane part it comes primed. But sometimes not. Or if a guy strips it down to the base urethane... then you want to start by using an adhesion promoter to 'bite' into the urethane, and then immediately follow up with your primer or sealer (if you're going direct-to-paint). The adhesion promoter sort of 'melts' the top surface of the bumper material which then creates a 'chemical bond' for the primer or sealer. Then you don't get any flaking off (in sheets) like you sometimes see with bumper covers in parking lots that weren't prepped properly. The paint companies sell adhesion promoter in cans or quarts, etc specifically for bumper covers.

HERE

HERE

is a kind of DIY product example. UPol and Bulldog ...and every paint company sells an adhesion promoter. And honestly.... for small projects I've sprayed out a wet coat of PVC pipe solvent from a spray gun (the 'clear stuff), which you can buy at the home center for $4 a can. You could maybe add in some slow reducer to slow it down to melt in better if you wanted. Sprayed a wet coat on ...allow it to soften the surface.

Once it's flashed off, then follow up with 2k primer. I use Nason generally. Then prep/sand the bumper as you normally would and paint. In fact I just did that here recently on my Jetta rear bumper cover. I've bought the PPG Bumper Adhesion promoter product for $100 a quart. It's basically a very aggressive solvent. To me is smells like and seems exactly like pvc pipe solvent ...so I tired that once just to see. Seems to work. But you ought to test a spot on the backside and make sure it 'softens' the material a little. Or use the SEM product.

If you're doing a small repair you can probably prime right over the bumper cover plastic ...but how small is small? But if it's large enough I'd squirt on some pipe solvent on the repair area. If you've already made the repair than forget about everything above ....lol.

Painted Item:
I don't usually use a flex agent. I haven't used any in years. Mainly b/c urethanes are rather flexible themselves and bumpers (especially old stiff bumper covers) don't flex a whole lot. But a flex agent painted part will fare better in a collision or when bent hard (but then you'll likely still have other damage to repair). Otherwise, just use whatever 2k primer you have over your repair area ...assuming you've sanded down and prepped the surface.

I recently re-painted my Jetta bumper cover which the topside I had to strip down to bare bumper due to the clearcoat went bad from age/UV. The top sides also were stripped. But the rest of the bumper cover I wetsanded down and feathered out to the bare urethane. In other words, I stripped off the crappy paint and wetsanded (feathered) the rest with like 400 grit. What I did there before painting was added a small amount of slow reducer to pipe solvent in a gravity touch-up gun and sprayed a wet coat on the bare bumper (not the painted area). It softened it up a little bit. Then I followed that up with urethane sealer and directly painted (no primer prep or sanding) since it was feathered pretty well. The solvent didn't lift the feathered paint. Seemed to work pretty well. Let's see how she looks in 10 years. I've done it several times in the past so I expect good results. I HAVE PPG adhesion promoter but they use a dye in it (like purple PVC pipe cleaner)...and I didn't want the dye on the rest of the paint.

I normally just use Nason 2k primer on most substrates ..bumpers too.

 

If it's a small repair area, try the witches brew PVC solvent. If it softens the surface a little.... let it flash off and put on your 2k primer. That'll save you a lot of money and fooling around.

Someone needs to convince me the PPG bumper A-P for $100+ a quart ..or whatever it is nowadays, which smells and seems EXACTLY like purple-dyed PVC solvent ....that it costs them anywhere near $100 to produce that!! There's probably $2 of product in that can. That's what gets my goat. But if I was prepping a brand new $600 C3 bumper cover (or any new raw bumper cover) ...I would definitely use it. And I did on my own C3 new bumper cover. Just because. But some of those paint prices now are eye-watering. I tried (tested) the bulldog adhesion promoter plus recently (one-step ..with sealer). I didn't end up using it. I need to test it a little more. Didn't seem to 'melt' into the bumpers as well as regular A-P or the pipe solvent. But again I need to test it a little more. There are videos where bodyshop guys swear by it.

Obviously adhere to all proper safety precautions whatever you do.

 

I use the same epoxy primer I use on the rest of the car

 

Thanks for all the information and wow didn’t expect such a quick responses. I’ll post a pic,it tells all. Front needs more sanding. Top has a lot of high lows that I can’t do much with and going to sand more paint off. Now the back one spot lifted so I sanded it and feathered it out. It going to need more work. Maybe spot that with adhesion promoter spot prime and paint rather than stipping the hole thing.

Paint lifted only one spot.

The gray is polyvance filler.

 

Kind of a toss-up there. I guess if it was me I'd do a test spot with the PVC solvent to see if it'll soften the bumper... put some in an inconspicuous spot with a small modeler's brush. See if it 'softens' the substrate a bit. If so, spray on a wet coat on the bare bumper areas with a small touch-up gun. Check to see if you need a 2nd coat (b/c it evaporates quickly). After it flashes off, apply your 2k primer. HERE Or get some of the adhesion promoter as I've linked above.

If you applied your 2k primer over what you have now it would probably be ok too. I'm sure they're good and stiff ...not very flexible anymore. But I like to get better adhesion on bumpers as much as I can.

.

 

You’re right about the cover being stiff. They’re real stiff. Have no cracks just wavy. Very hard to get it perfect. The car was in Florida for a while. Probably baked them. Thanks again for the advice it helps out a lot.

 

Well here's an idea:

You could consider applying 2k primer, then scuff it and apply a flexible filler over the bumper cover ...and sand it flat with a board sander. Use a flexible body filler HERE. Worth a shot. Its plastic over plastic. Silver doesn't really heat up like black or dk blue....which would expand/contract a lot more. I think you could maybe get away with it on silver ...if you are gutsy enough to try it. Like I say, use a flexible filler. Take the paint off the top and use an adhesion promoter (or the PVC trick) ....to get good adhesion with 2k. Then scuff and apply the flexible filler. I can't guarantee anything, bet it would last a long time ....sure look a lot nicer. Be Worst case, you sand it all off in 10 years and re-do it. I bet it would last a long time though. How often does the car see the light of day??

Most new fillers are designed to be used over (scuffed) primer anyway. But I would remove all that potentially old lacquer paint/primer on the top ...if you do it.

Are you going to blend back into the front of the hood/fenders? Or just spray the nose & tail?

.

 

I bought a brand new urethane cover for my car a while ago (like 15yrs) ...when Ecklers was still making them (maybe they still do??). For an 81. They're pretty good, but even those get a little wavy too. But that's how they were. Fiberglass is good until the nose gets tweaked ....and damages the fenders/hood. I guess if a guy has insurance...

 

Hey Walleyfisher nice paint job. That’s a lot of work stripping it down. Did you paint it where it sits. How on earth did you keep the overspray down. Everything looks so clean.

 

Your lucky. When I priced everything out I decided to stick with what I had. Even used fiberglass was expensive. I going to paint the whole car. Not sure if I’m going to stick with the 2 tone. Silver, charcoal or i’m looking into steel city gray. I visited a members shop in N.C. And he introduced that color to me. It really sticks out.

 

Mark I used polyvance Flex Filler 2 on the front. Sanded it with an air board sander. I’m going to do it one more time and try to feather those high spots better. I tried a little guide coat on it. Trust me that’s way better than it was. That filler is for urethane bumpers.

 

Ok....sounds good. Sounds like we're thinking along the same lines.

 

Thank you, I used a nice gun and wetted the floor down

 

if I can ask a few questions. much newer car 2017 aftermarket polyurethane bumper c7 z06. where does one start? I mean its looks ok in its raw state but do you fill the entire bumper? how do you spot any low or high spots? primer first then look for dark or light spots? go for the gusto and shoot primer then pain t then clear and hope for the best? as you can tell im not v very experienced in this art. torch red single stage paint

 

I’m no expert but the things I do know is you have to clean the bumper. Soap and water and a scotch bright pad. I wipe it with rubbing alcohol too.The new bumpers come out of molds with mold release coatings.You have to make sure it’s off before priming. Run your hands on it to feel for scrapes or other imperfections. If it’s new you shouldn’t have any highs and lows. Just check for marks from rough shipping. Cleaning is a big deal. My bumper in the picture is an old bumper that had waves from fatigue through the year. I got most of it out with a flexible filler. Polyvance. It works for small imperfection's too. It’s an easy mix equal portions. Then sand it.

 

this is exceptional !! even if I farm this out to a shop ill be sure to wash it and wipe it down prior to dropping g it off. im no painter but I might try this as a project and see what happens.

 

Sure why not.

1) Mask off the area really well (put plastic over the whole car if you're going to spray on the primer).
2) Soften the bumper urethan as I described above...(that's your adhesion promoter pvc trick)
3) Apply your 2k primer ...a couple coats. If there is not damage and it's just paint that flaked off.....you could brush the primer on with a foam brush. Let it sit a while, come back and build up with another thick coat. Or 3..
4) Let it sit a few 3-4 days to cure. Esp b/c it's brushed on. Even if you spray it on, let it cure out.
5) if you have any bodywork to do, then you'll need to scuff it up (sand it) with like 120#.
6) If you don't have any chips or gouges.... I would spray on a guide-coat ...which is a light spray of some paint....sandable primer is best. But for a small job like that, if you have some flat black paint around... mask off and spray a very light 'mist' coat of that on the primer. I would do that after your primer is applied so it can cure the same number of days you let the primer cure-out. The guide coat is to let you know when you've sanded enough...or if you need to sand more.

7) Wrap some 320 grit wet/dry sandpaper around a 3-4 or 8" long paint stick ... Make sure the paint stick is flat. Wrap the sandpaper around the stick and carefully sand the primer area trying to NOT get into the paint area. Or maybe you can start with 400#. Either way. Then switch to 600# when you get it all worked down smooth.
8) Depending how it goes, you could either apply one more coat of primer, or go right to the paint stage.

Paint stage
9) Before you begin you might want to figure out how far out you want to spray the clear. The reason for this is you'll ultimately do a 'blend' of the silver and spray the clear to wherever is convenient. And on a C3...no place is convenient. And since silver is one of the most difficult colors to match and blend...you almost ought to figure in doing the entire top of the tail and nose. And back-masking the edges .....and try to melt the clear in where the clear edges are. This is all kind of advanced paint work. Honestly you ought to be taking it to a shop. It's very unlikely you'll get it right the first time. But anywhoo....
10) Wetsand the top of the tail and the nose with like 600#.
11) Mask the car off really well other than the repair areas . You probably should factor in completely clearcoating the whole top of the nose, and maybe the top of the tail. You could do a smaller area....but if you want a seamless blend???
12) Apply your basecoat. I would go real light on the first coat...and not even put on a wet coat. In fact you might just mist some on over the primer ...and leave it for 10-15 minutes. The reason is... if you just go and put on one wet coat right away, there 's a good chance the solvents will 'lift' some of the surrounding primer area (meaning you'll see an unsightly halo where the primer edges are). By dusting it on and letting it flash off real well ...its less likely to do that. After your 'dusted-on' first basecoat flashes off, then come back with your first wet coat of base. Over the repair area. Give it plenty of time to flash off. You're in no hurry. Then another wet coat. Let it flash off a good while. You're trying to build the color up to match the existing silver. Silver is rather transparent so it takes a couple 3 coats. Probably need a third. I'm assuming you've tested the silver color before hand and know the color is right on. If not be sure to do that. The last two coats of base should exttend beyond the repair area. Once the base is applied, don't rub it, don't tack-rag it...don't disturb it at all, or you'll see rub marks (ugly) under the clear.

13) Clearcoat: Now is the time to put on the clear. If you back-masked the edges of the nose and tail... spray on a coat of clear. Let it fully flash off. Here is where you get your 2nd spray gun out and put some clear reducer in it...and have it ready.
14) Final coat of clear you want to pull the masking back and spray out to the edge, then afer a short few seconds, gently dust on some of the solvent on the edges using relatively low pressure....to melt the clear into the rest of the paint. Probably even along the entire back half of the tail where your blend line was. A C3 has to be the toughest car to blend b/c there are no real 'lines' to paint to...like most vehicles.

Watch some 'blending' paint videos.

Once it's cured in a couple days...you can maybe buff the edges of the repair.

Like I say, you're almost better off taking it to a place ...esp if you don't have any of the paint supplies. You'll spend half of what a shop will charge just buying supplies. Don't even *think* of doing it with part's store spray can paint. It'll turn out crappy. Dive er over to Maaco and see what they'd charge. (seriously). Then you know it'll more than likely turn out nice w/o a big dark spot of dark silver there on the bumper ....or a bunch of tape lines. If it looks good, you''ve added value. If it looks like crap, you've reduced the value (some) and potentially wasted time and money. At least made a buyer wonder what else is "quickied".

It's an easy fix to a guy who's sat in the seat.... if you know what I mean.

Good luck!!

 

its a new in box bumper off the car raw material zero materials on it. I have a spray gun compressor and materials just need the paint primer and sealer

 

For a fresh bumper, wash it off real well with warm soapy water. Let dry completely. Mix up your urethane primer, yeah you can use epoxy too, or urethane sealer ..either. Spray on adhesion promoter... something like should work. Your local paint and body store would probably have it too. Get enough on. Check it to see it's doing what it's supposed to do in terms of softening the bumper surface. Then follow up with the primer/epoxy/sealer (whichever you plan to use)

If you are going to wetsand and make the bumper 'great' then use a 2k primer. If you have the rest of your car ready to paint and gong to paint right over the bumper cover ....w/o doing any sanding work, then before you go to seal your car, apply the adhesion promoter, then apply the urethane non-sanding sealer. I suspect you'll probably put on a primer so you can work out any imperfections in the surface.???

You don't really *need* flex agent, urethanes are flexible enough to handle quite a bit of flexing. But if you use it on the primer, it will help prevent cracking a bit better under a HARD flex...like if you run into something and it gets pushed in quite a bit. I haven't used flex in a couple decades, I didn't use it on my 81's nose, nor another bumper I just did. But then I don't run into stuff either. I probably wouldn't use it (myself)...but I hate to recommend to NOT use it. If you hit something hard enough to crack the urethane paint, you'll likely have scratches and gouges to fix anyway. But like I say, if you use it on your primer...the primer ought to be uncracked under a hard flex. Paint I wouldn't use it on...due to it's affect on colors. But for SURE use adhesion promoter to soften the urethane (test it beforehand to make sure what you buy is doing the job), or the primer will eventually flake off in big pieces like those ugly bumpers you see flaking off 2" square pieces...at the parking lots you drive through ..sometimes. (a result of bad prep-work).

Let us know how it turned out

.

That should do it. IfShow us how it looks when you get it on.