4 replies to this topic

[Mito]

When painting the underneath of the car, I intend to do the following:

1. 2 coats of epoxy mastic (7hours apart)
2. seam seal (Bilt Hamber brushable and tiger seal) - next day >7 hours after the last coat of epoxy mastic.
3. Stone-chip - 3 hours after seam sealing
4. Top coat - when stone-chip is tacky 

There will probably be around a 12-24 hour period of time between the last coat of epoxy and the stone-chip.

 

Do I need to re-key between any of these stages or am I okay to apply the next layer without re-keying?

 

How long can epoxy be left for before it has to be keyed (I can't find anything in the Bilt Hamber docs)?

 

 

[Ben_O]

You dont need 7 hours between the coats of epoxy.
It just needs enough time to flash off between coats.
This depends on the product used and the temperature but as a general rule of thumb, it just needs to be touch dry.

Once fully cured, you will need to key up the epoxy. It can be sanded if required, or just use a scotchbrite.

Then do the seam sealer.
You don't necessarily need to wait for this to fully cure before going on with the stonechip but it doesn't hurt. At the minimum, wait for it to skin over.

The stonechip will dry very quickly but as long as it hasn't fully cured before applying the top coat, there is no need to key it up so work fast at that stage.
Hope that helps
Ben

Edited by Ben_O, 02 May 2021 - 11:17 AM.

[Vanman20]

With the epoxy primer I use,Lechler,it takes 48 hours to fully cure ..... I've sprayed stonechip over it in the first 24 hours and it cracked.
I'd read all the tds for each product before you start

[Mito]

With the epoxy primer I use,Lechler,it takes 48 hours to fully cure ..... I've sprayed stonechip over it in the first 24 hours and it cracked.
I'd read all the tds for each product before you start

It states 7 hours for it to be hard dry, retarded when temperature below 10 degrees

[Ben_O]

With the epoxy primer I use,Lechler,it takes 48 hours to fully cure ..... I've sprayed stonechip over it in the first 24 hours and it cracked.

It states 7 hours for it to be hard dry, retarded when temperature below 10 degrees

Ok so that's the full cure time. You don't want to leave it to fully harden between coats otherwise the next coat won't adhere properly.
The idea with multiple coat applications is to only allow each coat to 'flash' before the next. Once you have applied the recommended number of coats, then you can wait for it to fully cure.
I'd read all the tds for each product before you start

Edited by Ben_O, 02 May 2021 - 03:42 PM.