Over coating times

[ChrisBailey]

Hi all,
I'm painting my fibreglass car. I'm using polyurethane paint from TA industrial paints.
The bits I painted so far, I sprayed the primer and waited 12 hours then block sanded with 180 grit and finally sprayed the top coat generously.
I have some difficult bits next such as the doors, I need to paint both sides so if I did the same method, it would take me 4 days since I lay them down flat on trestles and can only do one side at a time.

I read the primer says it has an over coat time for top coat of between 1 and 4 hours. If you go past 4 hours you must wait 12 hours because it can attack itself.
Does this mean I can paint the colour top coat after primers dried between 1 and 4 hours?
That would half the time it takes me.

This is the primer.

Fibreglass Primer - Fibreglass Primer Paint | TA Paints

Fiberglass Primer is a compliant high build one pack primer offering enhanced anti-corrosive and fast drying properties to metal.

www.taindustrialpaints.co.uk

Thanks

 

[steveo3002]

sounds like you top coat between 1 and 4 hrs or after 12 hrs

fibreglass paint thats anti corrosive ? must be some good gear eh

 

[norsa]

Couple of things Chris. Did you say you top coat on 180 grit? The drying curing times can be confusing for sure and many manufacturers have their own slightly different drying times. Ok. Drying times are generally given at a temperature of an ambient temp of 20 degrees C. There normally would be four states of dry on the TDSs No1 Flash off. The time to apply the second and if necessary third coat. Polyester base coat being much shorter than DG. Then you have what's called wet on wet drying times which is the most time you can leave a coat before you can apply another coat and get intercoat adhesion. Outside this window is the cure time where you need to provide a mechanical key for subsequent coats. I'll not go into fully cured for nib and polish or bake times at 60' or latterly I.R drying times. These are more relevant to commercial shops for fast throughput. Wet on wet is generally relevant to top coat over primer and is really more suited to maybe interior parts and those not really on show of the external vehicle. My best advice. Cure your primer fully as in a few days to stop shrinkage. Flat back through the finer grades to 6-800, no finer and apply two to three coats of DG or Clear in COB and in the case of polyester base coats, sufficient to hold out the colour then an immediate drop coat.
A lot of info there but always happy to answer questions. There are no stupid questions either as they tend to be the questions other fear to ask so blunder on and have to ask how to rectify the problem.
Nick

 

[ChrisBailey]

Thanks for that info.
I'm a complete amateur and I'm spraying this DIY in a make shift paint tent.
I will paint the inside of the doors by priming and then top coat within the 4 hour window. I realise it's shorter due to the heat.
For the outside, I'll let the primer cure and then flat it before the top coat, I'll do it over a few days.
I did use 180 grit to flat the bits I painted so far. I'll go finer grit next time.

What's the benefit of finer grit blocking?
The paint I'm using is glossy, I'm not sure if it needs a clear coat. How do you know?
It's supposed to be for boats and used above and below the waterline.

 

[norsa]

I can't comment on your specific paint. I only use one manufacturer for my paint which is all 2k. If your paint is thinned 1:1 it's probably a basecoat and requires a clearcoat virtually immediately after flash off. It will dry quickly to a satin finish. If it contains 5 to 15% thinner it's probably a Direct Gloss. It will dry with a gloss finish. Flatting provides a key and removes the previous scratches so if for example you are applying an epoxy primer, you would prepare the substrate with 120-180. I prefer the latter. If you put a top coat on that, as it cures, it will sink back and show every scratch. To eliminate this, you need a finer paper to remove scratches but it's important to do it in stages. I would maybe flat my filler back with 80 then double the grade each time to get to my perfect substrate for top coat. IE. 80 120 240 400 prime 600 top coat.
Nick