I've asked this on PBO but...

[CharlesSwallow]

...I need an early answer

Owatrol as a Primer After Grit Blasting

"...any thoughts? Is it better to get a coat of epoxy on first or go with the contractor's advice and use Owatrol as a first coat primer. He is just doing the blasting of the cast iron keel; I'm doing the rest but have prevoiusly found Owatrol to inhibit the adhesion of subsequent coats of epoxy. can't decide; need to by Sunday!

Chas

 

[ianabc]

Grit blasting ferous metals...

Grit blast to white metal,

Blasting grey metal will not hold paint as well

Without touching and adding grease from hands

Paint immediatly with zinc rich primer, at least 2 coats

80 percent zinc is good

NOT spray paint for cars though

Let dry

Paint with epoxy prob. 3 coats

Sail

 

[Pasarell]

Blast Primer

Owatrol is a very good product in the right places but would be a lousy choice as a blast primer under epoxy. Epoxy will not sticj to the Owatrol very sell and it will also affect adhesion of Owatrol to the cast iron. The worst of both worlds.

On cast iron I would always go with a zinc rich primer. It is difficult to get the metal completely clean, dry and salt free so zinc will be the best way to delay further corrosion taking place. As the previous poster states get the metal blasted as clean as possible although white metal will not be achievable. In my experience people who blast yachts know little about blasting standards although many will talk a good talk! Ideal is to blast it clean, pressure wash with fresh water to remove salts and then abrasive blast again although this may be a bit pricey.

A good marine grade zinc primer is ideal but you can only put an epoxy over if it is an epoxy based material. Urethane zinc primers, followed by urethane underwater primers will be just as good - and more forgiving when applying - than epoxies. Just less well known in chandlers.

 

[vyv_cox]

Owatrol is a very good product in the right places but would be a lousy choice as a blast primer under epoxy. Epoxy will not sticj to the Owatrol very sell and it will also affect adhesion of Owatrol to the cast iron. The worst of both worlds.

On cast iron I would always go with a zinc rich primer. It is difficult to get the metal completely clean, dry and salt free so zinc will be the best way to delay further corrosion taking place. As the previous poster states get the metal blasted as clean as possible although white metal will not be achievable. In my experience people who blast yachts know little about blasting standards although many will talk a good talk! Ideal is to blast it clean, pressure wash with fresh water to remove salts and then abrasive blast again although this may be a bit pricey.

A good marine grade zinc primer is ideal but you can only put an epoxy over if it is an epoxy based material. Urethane zinc primers, followed by urethane underwater primers will be just as good - and more forgiving when applying - than epoxies. Just less well known in chandlers.

Good advice. Go with it.

 

[CharlesSwallow]

Owatrol is a very good product in the right places but would be a lousy choice as a blast primer under epoxy. Epoxy will not sticj to the Owatrol very sell and it will also affect adhesion of Owatrol to the cast iron. The worst of both worlds.

On cast iron I would always go with a zinc rich primer. It is difficult to get the metal completely clean, dry and salt free so zinc will be the best way to delay further corrosion taking place. As the previous poster states get the metal blasted as clean as possible although white metal will not be achievable. In my experience people who blast yachts know little about blasting standards although many will talk a good talk! Ideal is to blast it clean, pressure wash with fresh water to remove salts and then abrasive blast again although this may be a bit pricey.

A good marine grade zinc primer is ideal but you can only put an epoxy over if it is an epoxy based material. Urethane zinc primers, followed by urethane underwater primers will be just as good - and more forgiving when applying - than epoxies. Just less well known in chandlers.

This is the traditional view, with which I have always agreed. However, Owatrol CIP, this stuff:- http://www.owatrol.com/index.php?langue=en&page=produits-rustol-cip

appears to be rather different.

I will only arrive at the boat at Sunday lunchtime and the contractor is doing the job starting at 0900 on that day. I therefore don't want to leave it unprotected in sea air until monday, the earliest I can get any protective coating on myself. Problem with the very high zinc content paints is getting them to stay on and they aren't always a good key for epoxy.

Chas

 

[vyv_cox]

I've read their info and they certainly state that it should be OK beneath epoxy. I would prefer a two-pack primer myself to be sure of good adhesion with successive coats.

You are correct about the time lapse - primer coat needs to be on in under an hour from blasting.