Ok, I have been searching threads and the internet without finding real definitive answers. Of course, that may be because there is none. So, checking again.

My original urethane fascia is in pretty bad shape so picked up a doner. it was underlying black with gray rattle can primer over the top.. After trying every known stripper and hand sanding, nothing would touch the original factory paint under the rattle can stuff and hand sanding was going to take a lifetime. So, since this is a doner anyway, I decided to go with 80 grit on an electric orbital hand sander.. Most of it is currently stripped to bare urethane successfully. Now for a few questions.

1) It appears that the factory original paint had a black primer under black finish.. Was that typical to use primer color same as finish? Maybe so rock chips to not show up? Should I dye my primer to black since that is my finish color??

2) Bumper prep I am going to use Bulldog Adhesion promoter before primer, especially since I am down to bare urethane.. Now for the controversial primer question.. I am going to use Deltron DBC top coat system for base and clear. The paint shop recommends K36 urethane primer. Is that the correct primer for urethane? Although I don't see a lot of scratches or even swirl marks in the urethane, I do see what looks like light spider cracks in a few places but that may only be discoloration of the urethane from the spicer cracks in the original top coat.

3) So, my build up would be: Adhesion promoter, K36 Primer, Deltron DBC base in black, then Deltron Concept 2000 clear. Do I need to put a high build primer like K38 between the K36 and DBC base? Do I need a sealer over the K36 and/or K38? PPG tech sheets aren't clear on these questions.

4) I haven't found a clear answer on flex additive but thinking about it for the base and clear. Doesn't sound like the primer(s) need flex but, if I am going to use it, should it be used on the primer too?

Thanks..

 

1: I'm not sure, but I'd dye my primer black so you wouldn't see chips.

2: I'm not familiar with K36, but if its an epoxy than I'd certainly go for it, it'll reduce rock chips too from what I've heard from the hot rod guys.

3: If you do put a high build, I'd put flex agent in it and keep it very thin, ask me how I know >.> Other than that, it sounds like the right order. I like to use sealer, but you shouldn't have to do that at all if you're just using one type of primer - just keeps body filler from haloing and keeps everything a universal color.

4: When I used DCU 2021 clear, it said flex was only required when painting the bumper off the car, nothing when it was mounted. No flex should be needed in the base, but I'd put flex in the primer. Just as a little extra insurance, you know.

 

I do not know about orig. primer.
I have done what you are suggesting but I use a d/a sander.
k36 is a high build primer unless you reduce it down and must be sanded before base coats.
You should be able to get a tech data sheet from your supplier.
I dont use flex agent myself.

 

The K36 is a urethane primer.. I have DP90 epoxy primer but I am thinking its better to use urethane on urethane.. I am planning to paint it off the car since it is my daily driver so I can do a quick change out.. I may just use flex on the clear.

Another question, the fascia has a couple of small scratches so what kind of filler is best for flexibility? Should it go directly on the urethane with or without adhesion promoter or on top of the primer?

Thanks...

 

Epoxy is good for adhesion but not very good with UV (sunlight).
I have used both but prep is more important than chemistry in this case.
I have used maxim and sem flex filler with good results, just follow the instructions.
I think some vids are available on line...

 

I think you might be going overboard. I redid mine with some adhesion promoter, shopline 2k primer, basic red base, and clear. Looks better than the rest of the car.

 

Well, it is getting a little expensive.. I know I am using high quality components but they want $50 for a pint of the flex additive.. I may have just a little bit of it so will have to see if I can find it (moved recently).. But think I am going to paint it on the car so I don't have to use it.. Paint shop says its only needed if I paint it off the car and I have always had good advice from these guys.. They don't think I need to use the DP90 as a sealer coat over the K36, DBC can go directly over it..

 

Originally flex additive was designed to make the paint flexible long term. Now most flex additives for urethane paints evaporate out over a short period of time. It's designed to give you a small window of time to get the bumper installed. My belief is that most fresh paint has enough flex to work with it without damage and flex additive won't last long term so why bother. New plastic bumpers are made from other materials and don't flex the same as our older urethane covers. 3M used to make an alcohol based coating for urethane bumpers that was an awesome product. Being alcohol based it didn't react with the plastic and was as close to factory primer as I'd ever seen. Of course it was such a great product I don't think they make it anymore. But with current primers available I'm not sure it's needed anymore. So with all that said ... believe what your paint store tells you. Don't mix brands, use a system. Some paint company spent a lot of money making sure there system works. If you mix brands you just gave up any rights you had to getting help if something fails.