Spray paint woes

[Bryce]

Hi,
I'm trying to refinish the front grille as it had been previously painted which was flaking off.

Spoke to a autoparts guy who suggested sanding it down spraying plastic primer then finish with black.

The problem is the black paint and some of primer on closer inspection seems to be reacting with something on the plastic, causing it to act hydrophobic at certain points but fine at others.

I've tried wiping it down with alcohol and just respraying when dry with the same
results

I've attached some photos if anyone can suggest a fix it would be much appreciated cheers

[davidoft1]

Going to need every spec of the old paint removing to stop the reaction

[Bryce]

So it's a reaction between old and new paint? I thought I had done a good job getting off but obviously not!

Any way of testing its all off before I try and respray again?

[Oldiebut goodie]

I sandblasted mine before I painted it.

[Bryce]

I emailed a few places to ask about getting it sandblasted but nowhere got back to me.

I assume not worth their time for such a small piece.

Wonder if sanding it all back then taking a torch to it will sort it, seen a video of it being done to plastic stadium seats to bring the colour back out

[tobydog]

Soda blasting?

Paint stripper?

?

[Bryce]

I was worried paint stripper might react with plastic itself.

I've tried contacting local soda blasting places but none have got back to me and their websites look like they focus more on big projects.

I tried using a dremmel with a brass brush but it seemed to melt plastic from the heat

[AngeloEvs]

Flat and apply Isolating primer first.

[diabolov]

Be cautious of any fluids you put on these as they are ABS plastic and solvent could/will melt them,
so will the heat from aggressive sanding, such as the Dremel, as you have found out 

Make sure your paints and primers are of the same type eg: acrylic, cellulose. as these react with each other too.

 I would sand down apply acrylic plastic primer again and make sure that is stable and dry, lightly sand down then
 blow down with an airline or wipe over with a tack cloth. Don't wipe over with white spirit or meths, then go acrylic top coat. 

M