Paint Compatibility Problem?

[stem]

I recently noticed that the underneath edges of the wheel arches on my 2006 Mazda 6 were starting to rust slightly, so as I had done with previous vehicles I rubbed the rusty area down and applied a couple of coats of Hammerite to give some protection against stone chips. After a few days I gave the Hammerite a light rub down and applied a top coat of the cars colour (Blue Mica) that was mixed at a local motor factors, but it seems to have reacted with the Hammerite and gone all wrinkled. So I rubbed it all down and tried again but the same thing happened

As I mentioned before, I have done this on my previous vehicles and never had a problem. Any ideas? Is there a primer I could use between them that would be compatible with both paints?

 

[Burnerman]

Your car's touch up paint is likely to be cellulose, whereas Hammerite is xylene based.....the two don't mix.
Barrier primers are available, but you could try rubbing the Hammerite away, priming the area and then add the body colour.
Add Hammerite after if you want for extra protection, but personally I don't rate it very much.
John