Barrier coat.....time between coats

[kito]

I am looking for advice. My project boat came with 2 coats of barrier coating but was never painted. I am guessing it was applied maybe 3 years ago and has been on the hard. The PO did a crappy job of fixing some blisters so I ground them all out and will fix properly. I will need to apply a couple new coats of barrier. Question is, what kind of prep work if any is needed to apply new barrier over an existing old barrier coat?

 

[jibes138]

Sand it to roughen up the surface for good adhesion. When applied fresh you will get chemical bonding between coats if applied at the correct time interval, but once fully cured you are dependent on secondary adhesive bonding. Remove all sanding dust and maybe wipe it down with acetone to make sure it is clean of all residue before applying additional coats. Note the original first coat of barrier coat going on the hull is also dependent on adhesion so the process should be the same as the directions for applying to a new bare hull. Just read the label on the can and follow the directions.

 

[Capt jgw]

And some of them are a real b***h to sand so be prepared for that. Very hard surface.