Cracking Paint

[gwiz22]

I painted my engine bay a couple of years ago. But recently had to take the engine is out again so I decided to clean up and paint the RHS of the engine bay which had got a bit messy. The previous painting was done with aerosols after rubbing down, a primer coat and then satin black. I repeated the procedure again this time, rubbing down and using the same primer. However, after the primer had dried, cracks appeared in the surface of the paint. So I flatted them off and primered again. Cracks appeared again. This time I gently flatted them off and sprayed the satin black. However, after the black had dried the cracks were even more widespread than at the primer stage. Anybody had this experience? any idea how best to remedy it?
The primer is Tetrosil Trade Spray and the satin black was from Halfords.

[Rob P]

That looks like the paint you are using is reacting to the paint below, have had this happened to me a few times when refurbishing Classic mini wheels.

[Craven]

Steer well clear of Tetrosil, I?ve found it incompatible with almost all other spray paints, just the sort of problem you have.
Ron.

[jeff jackson]

as answered, your paint is reacting to the paint below.
Two ways to fix:
rub all the layers of paint off, and then re-paint, hard work...
Or get some bar coat from a paint supplier. Normally you would apply this with a paint gun and compressor, but you might be lucky to find a distributor who can put it in an aerosol, or supply the bar coat in an aerosol.
Spray this on first, then your top coat on top of that.
Comes in a fetching shade of hearing-aid beige.
Hope it helps.
Jeff 72+2.