what is wrong with my spoiler?

[Mike PhillipsMike Phillips is verified member.]

I've seen this defect pattern in fiberglass and urethane rubber components before and could never find a term that describes what the problems, for lack of better terminology I called the defect we're seeing simply cracks in the paint but that doesn't really do the defect justice.

Micro-splits sounds good though...

What you have on that spoiler is actually millions of fractures in the clear coating.

Another good word...

Fracture. Fractures. Fracturing.


Clearcoat Fracturing

Clearcoat Failure

In your particular case, my theory is that you have a spoiler that is subject to expansion and contraction due to temperature changes and has been sprayed with a clear coat with no "flex agent" mixed into the paint

Or the service life of the flex agent that was added has quit working....

There's a lifespan to UV inhibitors in clear coat paints, I'm not a chemist but my guess is that nothing lasts forever so at some point in time it could be that the performance of any flex agent originally mixed with the clear that was sprayed has been reduced or diminished.

 

[Setec Astronomy]

The other issue that I have seen and we have discussed on different forums is that painted plastic and fiberglass parts seem to have a shorter paint lifespan than their adjacent metal parts.

When we've discussed this on other forums we talked about whether this is because the paint is different on the plastic parts, either just different or that it has platicizer in it, or whether it's because the thermal conductivity of the plastic is lower, allowing the plastic parts to get hotter in the sun than their metal counterparts, or some combination of both.

Possibly the higher CTE (coefficient of thermal expansion) for the plastics also plays a role as discussed here. There is definitely some difference because the painted side mirrors and (factory) deck spoiler on a car I used to have failed before the rest of the paint, and I have seen this on other cars as well.

 

[timaishu]

Wow. Thanks for the responses you guys. rops:

So to make sure Im understanding. Its the clear coat that is fracturing from thermal expansion of the fiberglass and the flex agent has failed causing the cracking?

The spoiler itself isn't cracked right? So it could be repainted?