primer cracking like mad

[skikman]

hi folks.i bought a yamaha fj1200 that was painted matt black.i want to do it in gloss black.i striped it down and sanded it.dont think it needs a prime coat as its pretty good,except for the belly pan which i have repaired,sanded and used a can of carplan hi-build primer.it cracked all over the place.not just the primer but through the matt to the original blue.sanded it down again and used plastic primer.went on ok but it is clear.so put the grey primer on it the next day and it started cracking as i was spraying.wtf is going on?

[stickybackbob]

The paint is reacting either to previous layers or to the plastic base. For plastic surfaces, running a blowtorch quickly over them and then wiping down with a solvent can get good results. For previously painted surfaces,an isolating paint may be required

[gavcarter]

get a power sander of some description, orbital , palm sander etc drill attachment and strip the whole thing back to bare plastic with 320 grit paper.

Give a good wash down with pre-paint panel wipe etc then start with a plastic primer. i would skip the high build primer unless you need a lot of little holes filling.

2 or 3 coats of normal primer with a light sanding of 600g will give a good firm base to start the colour on.

[Tamsin]

I agree with sticky.

Its a chemical reaction between the two paints, best thing to do is take it back to bare and start again...

[misscrabstick]

yep, reaction between paint products that do not agree with each other, you can buy isolator for spray guns that seals off the base layer from additional layers and stops this, don't think there is an aerosol equivalent though, rub it down to the plastic and start over.

[skikman]

thanks guys for the info.will sand right down and start again.i am going to use an air gun for the base coat and clear coat on everything.i have 2 pack paint.do i need an isolator for this?if so what do you recommend?

[gavcarter]

[sidewinder]

2 pack you'll need a ventilated face mask.that stuff is bad if you breath it in

[lihp]

This is far far easier to fix than everybody is suggesting.

Sand it back to remove all paint defects.

Leave for 24 hours and re-check for defects, then paint it with BARCOAT ISOLATOR (this will prevent the reactions) Then once that has cured paint whatever you want on top.
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[skikman]

[gavcarter]

[lihp]

[gavcarter]

[lihp]

[skikman]

[stinkwheel]

Could just be over-eager for the re-coat too.

I've had a second layer of paint crack up on me after putting the first layer onto dry, bare metal with a rattle can. Nothing there for it to react with other than the first layer of exactly the same paint which went on smooth.

Pure impatience, I should have left it a few days before re-coating.
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[lihp]

[stinkwheel]

[lihp]

Reactions don't always happen instantly though, and can take a few days even depending on the paint used. Any reaction will affect all layers above it.
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covent.gardens: lihp is my most favourite member ever