I primarily paint smaller objects but use house of kolor KD3000 for my priming and follow that up with BC-25 or 26 and then whatever house of kolor i choose typically a kbc and then USC01.
I am a newb so be easy on me but i'm having some adhesion issues between my primer and the bc/mc. It seems if I dig my nail hard enough I can scratch off the clear and bc but the primer stays put.
Here is my process
sand plastic part with up to 600 grit, wash with hot soap and water and then blow the object dry allowing 15-30 minutes before applying primer.
Apply KD3000 as a primer sealer in the 4:1:2 ratio. I'm needing to keep my build minimal and the plastic part is pretty smooth to being with so the sealer portion has worked in my detail gun with 1.2 tip. I had contacted HOK about dry times and they had no issues with mixing the KD3000 as a medium build in a 4:1:1 ratio and treating it as a sealer either.

Wait roughly 15-930 minutes and then wetsand the primer with 600 grit.
I am having to wetsand the surface because i get some dry spray. I know I know i should use a big gun but I'm talking about painting a cigar shaped piece of plastic and only use about 1 tblspoon of primer at a time.

after wetsanding I wash with hot soapy water and again blow dry the object and allow to sit for a couple minutes while I get my basecoat and color ready to go. Then I apply my basecoat and color giving proper flash times between coats then my clear. Finally baking at roughly 140 for 1 hour.

Ya'll are going to tear me up I know but where in the primer to basecoat process am I going wrong?

Should I only sand up to 400g? Should I not be wetsanding the piece so soon?

Any help will greatly be appreciated from this newb.

Use slower reducer in your sealer so you don't have to wet sand it.
Let it flash and apply your base. Then clear. You should be fine.
Are you not using a plastic adhesion promoter ?

You should try some CPS2035 Valspar as a sealer. It is epoxy I think you will like it better

Thanks. I'm already using ru312 as my reducer and i haven't found a way yet not to need to wetsand. The plastic parts have small raised fibers almost even after sanding to 600 grit. Im sure a high build would hide them but then i get into to high a build issues for final assembly. It isnt that hard to wetsand although im wondering if wetsanding si quick and washing is causing the issue. Hok tech sheet states sandable after 15 minutes.

I am not using an adhesion promoter and haven't found i dont need it with the kd3000 direct to plastic

you say you're only using a table spoon of primer at a time ? How are you mixing it ?

Using measuring spoons. 4tsp kd3000, 1tsp kda3000, 2tsp ru312

that does not sound like a good way to mix...

my advise would be invest in a smaller digital scale and mix that way.

if it was me i would use lacquer primer,

but before i recomend that what are you painting exactly ?

PainterDave wrote:if it was me i would use lacquer primer,

That is absolutely the worst thing to use, especially
on a flexible part like plastic.
Lacquer is known for its easily chipping issues.
It's brittle.
Another reason no body shop uses it anymore.

If you're having adhesion issues a epoxy primer is the strongest
and most flexible primer out there.
Since I started using epoxy on my bumpers I've reduced the road rash
almost completely.

Thanks guys the adhesion issues are between the epoxy primer and base coat. It isn't peeling off i just want the bond to be stronger

I don't know what it is your spraying, but if your sanding your sealer then maybe spray a light coat of sealer at the 4-1-2 just before your color coat. wet on wet as sealers are designed for is going to have your best adhesion. i would experiment with my gun to get it setup to spray better.
Jay D.

clark he is not having sealer adheasion issues.

i use lacquer primer every day. i do not use it as a build primer and if done correctly it will hold, it will not flake, it will not fail, and i use it in certain situations. in this situation i would use it.

sand small plastic part with 600

one light coat laquer primer

sand 600 this will stop all those little furry hairs he is getting

seal kd3000

flash 15-20 min

basecoat and clear

it will work