Anyone know what would have caused this paint defect?

[Iamzod]

I know there are a few on here that have painted cars before so I wondered what may have been the cause of this paint defect & how far back should I be going before prepping for new paint?

Some sort of micro blistering appears to be the problem, this is a 9 year old paint job but some traces of blistering started to become visible after about 2 years. On horizontal panels the blisters are more dense & the shine in the paint has vanished, it's almost Matte.

You can sort of see them in the reflection here-









The blistering appears to go back as far as this sandy coloured layer which I'm presuming is some sort of barr coat which appears to be on top of an older layer of top coat, looks to me like the primer is not adhering to it correctly for some reason. Can I stop here or do I need to go further back?

 

[RenoRanes007]

Do you keep it under a cover? If so it's a mixture of trapped moisture, temp and the car cover rubbing, one of my old cars started to get the same after spending a very wet/snowy winter under a supposedly good car cover.

 

[Iamzod]

It did get some very short periods under cover. However it's still been getting worse and it's been indoors for 2 years.

 

[doll]

This would have been moisture on the panel during the metal to primer, or primer to topcoat stage. Doesn’t really happen with newer refinish techniques - but I’m guessing it's on the Capri, which would have more than likely been painted (or repaired/resprayed in it's lifetime) with Cellulose.

Whether the car was covered or not, the winter months are the worst for moisture and they don't tend to dry out (unless they are in the odd bit of sunshine we sometimes enjoy in this country!). The moisture penetrates the paint layers and causes the blistering.

Unfortunately, the only way to truly eradicate the problem is to go back to metal.

 

[Iamzod]

It has been painted in the past, always in 2K though.

The bonnet was a brand new panel still in factory primer which was fitted in 2005, that has blistered too so it has to just be down to this most recent layer so surely if I go back as far as the last layer of top coat it should be fine?

I do want confirmation though as I don't want problems a year after painting.

Could there have been moisture or contamination in the air lines or compressor when the primer was painted on which would cause separation?

When done it will spend winter months in a carcoon & won't be allowed out to play in the rain.

 

[snapdragon69]

Sparks from a grinder or welding a long time ago?

 

[doll]

I can imagine your frustration!

I would say it was fine to go down to the primer layer, if the bonnet was primed at factory. It can be difficult when you cannot be sure which layer is contaminated. Obviously, going back to metal would be the best position to start from, as you can be sure it is free of anything that may cause issues again.

Moisture in the air lines is a possibility - where was it sprayed? Lines and compressors should be drained daily in a bodyshop and the air filtration systems should have regular maintenance to keep air moisture down.

As this painted with 2K, the blistering can also been down to curing times between the layers, or differing brands of solvent and paint. In which case none of the above would apply, as standard prep would be fine to rectify the problem. If it is moisture then it is actually caused by osmosis from air and exterior panel moisture, to the trapped panel moisture. The water forms the blisters - so the key is correct paint application.

Did you supply the paint? If so, was everything the same brand?

 

[Iamzod]

I didn't supply anything, I just used a local place that some posters on various forums had said were decent. As it was my first car I just sorta threw lots of cash at it & told them to sort it as I had no idea what I was doing, different story now as unless I paint it myself I'm only letting someone I know who restores old MG's do it, and even then I want to be involved in the process.