New epoxy paint over old epoxy

[eddystone]

I have to see if I can find any documentation but I believe below waterline was epoxied with 2 pack c.2007 although it could have been earlier than that. It appears to be sound and my expectation is that after sandblasting it will still cover 95% of the hull. If any large patches come off it is likely to be on the rudder and keel.
I want to "refresh" the epoxy layer before anti-fouling by applying 2 new coats of 2 pack to the entire hull/keel/rudder below the waterline. I thought Gelshield 2000 because it's the only one I've heard of.
1. Will new paint stick to old? (it will be a bit roughened up by the blasting process)
2. Do I need metallic primer between new epoxy and new anti-foul?

 

[CrikeyChris]

International recommends at least 5 coats of Gelsheild 200 if you are using it as a barrier coat - putting a impervious layer between the gelcoat and antifouling. Rudders are more prone to osmosis and because they are smallish it might be worthwhile to do the full 5 coats.
I think it will stick fine to the old epoxy but normal caveats the surface must be dry and very clean.
Gelsheild data sheets give overcoating times before applying their antifouling products - no need for an extra primer - gelsheild is the primer.
I've read articles warning of applying epoxy barrier coats if the fibreglass laminate has high moisture readings. Perhapsyou can borrow a meter?
I'm planning on applying 2 coats of gelsheild over an abraded Coppercoat and wait 5 days to let the solvents to evaporate and then applying a fresh application of Coppercoat. A grp professional recommended to me the two coats of Gelsheild.

 

[robmcg]

Nothing wrong with Gelshield but I would use Jotun epoxy - it's a fraction of the price and just as good.

 

[KAM]

I did that 12 years ago when I bought my boat. It was epoxied in 1990. I stripped the anti foul using caustic soda to check it and gave it another 3 costs of gelshield. If you anti foul whilst the epoxy is still relatively fresh say the next day you can apply without any other primer. It worked for me.

 

[Chiara’s slave]

I did that 12 years ago when I bought my boat. It was epoxied in 1990. I stripped the anti foul using caustic soda to check it and gave it another 3 costs of gelshield. If you anti foul whilst the epoxy is still relatively fresh say the next day you can apply without any other primer. It worked for me.

+1 for this. The Gelshield worked a bit too well as a primer for us, did it last year and have changed our minds and gone for copper coat. The yard are having not a lot of fun getting the new antifoul off. How they did laugh at us last year, when we had 20 years worth of antifoul to strip ourselves. I am maintaining a dignified silence.

 

[Refueler]

I've often found that epoxy based paints do not take kindly to old epoxy coatings .... they often require good clean and then sanding, wipe down - to provide a 'key' for new epoxy to 'grab' to.

In some cases I've seen where preparation was not quite enough - the new epoxy has lifted and can be peeled ... literally like onion skin.