Front and rear grill plastic questions

[Tony1968]

Getting these ready for bodywork and paint. My plan is to clean and degrease then go over all surfaces with 400 grit. Then use Bulldog adhesion promoter then epoxy primer.
Please let me know if there is anything else I should do or YOU would do. Aside from the cracking of paint they are in pretty good condition. I'm going by what I've read here but would appreciate more guidance. Thanks!

 

[Rktpwrd]

Those plastics are terrible to try and refinish and paint Tony. You’re definitely going to want to strip all the old paint off first. Even sanded, if you try and paint over top you’re going to see the existing cracks. It will be a huge waste of your time.

Also, skip the epoxy primer, try and get them as nice and smooth as you can in just bare plastic. 600 should get you there. More material on the surface will DEFINITELY equal the tendency for it to crack again afterwards. (I made the mistake of priming mine).

The plastic is horrible to try and sand, it has a tendency to ball up and/or leave a fuzzy texture. Wet sanding (in retrospect) might be effective in preventing this. You’re also going to need to use a high quality flex agent, it gets mixed in with the paint. This will allow for some flexibility for a period of time, but it eventually loses its effectiveness as the paint cures. Bulldog Adhesion Promoter is a definite must.

Even with all these precautions, my flexible plastics on Olds Cool have already started to crack too. Unfortunately I don’t know any good way to completely prevent it.

Good luck.

 

[Tony1968]

So no primer at all ?

 

[Rktpwrd]

So no primer at all ?

Correct.

 

[Tony1968]

I'm assuming that the color coat is better bonded to the prepped plastic. Very strange and glad I asked. There is too little out there about this procedure and believe me I've searched.

 

[Kamloops cutlass]

I don’t know if this applies to the situation or if materials are the same but I recently saw an 80s Camaro’s bumpers absolutely ruined by paint choice
Apparently some new paints don’t play well with older plastics or something like that
I know nothing about it , just saying that is something to watch for …( maybe? Lol)

 

[Tony1968]

Yeah this is going to be a tough one. I have high hopes and today I will attempt to completely strip to bare plastic. That's a ton of work! Oh well. My journey continues.

 

[Tony1968]

I don’t know if this applies to the situation or if materials are the same but I recently saw an 80s Camaro’s bumpers absolutely ruined by paint choice
Apparently some new paints don’t play well with older plastics or something like that
I know nothing about it , just saying that is something to watch for …( maybe? Lol)

Yeah this is going to be a tough one. I have high hopes and today I will attempt to completely strip to bare plastic. That's a ton of work! Oh well. My journey continues.

 

[Tony1968]

Donovan. The upper plastic around the headlights etc is a much harder plastic. The lower is the flexible stuff. Looking at pictures and I created a small divot in hard plastic. Not huge as I'm pointing to it but definitely feel it. My mistake. So now I'm trying to figure out what I can fill it with. I'm searching but not coming up with definite answers.
Also if you look where the cracking was after I removed paint you can still see cracks in bare plastic. Is there something I can use for both as filler? I have 2 part 3m glaze but it doesn'tspecifyuse on plastic

 

[57 Handyman]

Tony, DO NOT scratch the base plastic by using rough, low grit number sand paper. Take your time with a dual action sander. Those gouges and deep scratches will need to be covered/repaired which is the purpose for fillers and/or primers. There are specific materials for repairing different types of plastics. I suggest discussing your restoration project with a body repair professional or your local paint supply person. Another option for information is your local community college with an auto body repair program.

Good luck!