Painting Plastic properly...

Anything goes in the world of fiberglass and plastic

Posts: 7
Joined: Sat Jan 18, 2020 1:33 pm
Location: Charlotte, NC
PostPosted: Thu Feb 27, 2020 8:46 pm
My hood was recently replaced at a body shop while doing repairs from a tree-fall (long story).

The shop installed a used hood to avoid repairing the original aluminum hood. I ended up with a different styled hood, and I’m okay with that.

The problem is the plastic hood insert for the heat-extractor vent is faded and chalky. The dealership used a plastic treatment in effort to make it look better, but it didn’t help at all.

The heat extractor inserts (2) on my old hood were painted plastic and matched my hood perfectly. That’s what I want again...

The dealership body shop that performed the work said the part can’t be painted and refused to paint or replace it.

I ordered a new insert at my expense ($120) and it arrived today. The shop refused to paint it because.... Get Ready.... “Plastic Can’t Be Painted” :rotfl:

Never mind that I know plenty of Shelby owners who had their’s painted to match the hood, and avoid fading. Apparently mine can’t be...

So... I’m going to do this myself with rattle cans, but I want it to look nice..

My plan was to scuff the entire part on the exposed areas, coat it with adhesion promoter, then get a can of (color code matched) touch-up spray paint, and hit it with about 3 coats.

Someone else advised me that this plan won’t work...

This guy says I need to sand it smooth like a metal part, then prime with plastic primer, then spray a base coat mixed with a flex agent (I guess this means no rattle cans allowed) then spray with 3 coats of clear (I suppose that needs a flex-agent added too).

Can I just sand it smooth, hit it with adhesion promoter and use a normal 1 part touch-up spray paint? I don’t mind if I have to primer it, but what I thought would be fairly simple is starting to confuse me.

Thanks guys..

I’d attach a pic, but I can’t figure out how to do that so far.

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Joined: Sun Dec 16, 2012 4:46 am
Location: Canberra
PostPosted: Thu Feb 27, 2020 10:26 pm
Of course plastics can be painted, as you know. I'm amazed that people in shops spout such a load of rubbish, expecting the customer to believe it.

Both methods that you detail are essentially valid. Which one to use depends on the part, the type of plastic and the quality of that plastic.

If the plastic is good quality then it's not likely to be porous with the pores holding mould release agent that will stop the paint from adhering. In such a case you can scuff with Scotchbrite, wash with detergent and clean with an alcohol based cleaner before going straight to adhesion promoter and then a primer and top coats.

If the plastic is questionable then a special plastic primer is necessary, together with a specific treatment regime before application.

In your case, I probably would have just sanded the old part to remove any chalkiness, primed with a 2K primer and painted top coats. Forget about the flex agent - how much is a bonnet vent going to flex?

Matching the colour might be the difficult part. A pre-mixed, off the shelf can like Dupli-Colour probably isn't going to be a good match, even if it's the same colour code. So, to get a better match you need to find a supplier who will match the colour visually and/or with a spectro, then put that in an aerosol can for you.

You don't say whether the colour is solid or metallic/pearl. If solid then an acrylic lacquer paint will be fine, if metallic/pearl then you'll need to clear coat as well.

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