Priming Steel for Epoxy Filler

[Amp1ng]

I have a 50p piece sized lump of material missing from the starbourd bilge keel face which a surveyor assures me is slag inclusion from the casting process. He has suggested that I clean out all traces of corrosion from the area, etch prime, prime, fill, prime and antifoul. I have etch primer fluid already but I was planning to purchase a pot of Primocon to prime the metal following application of the etching fluid then use a standard epoxy filler before rubbing down and coating agian with primocom and then two coats of antifoul.

Does this sound like the right materials to use and the correct process to follow?

 

[KellysEye]

To stop rust the first coat should be zinc rich epoxy.

 

[vyv_cox]

I think that for best results it's best to stick with epoxy throughout. I'm not sure of the value of etch primer on steel but if you Google 'etch primer vs epoxy primer' you will find as much information as you could possibly want, mostly from car body people.

 

[Pasarell]

Priming steel

In an ideal world you would go with a zinc rich high performance primer first but unless you can clean the metal to a high standard there isn't any point. It is unlikely you will have an area that size blasted and if it is any depth you won't even be able to grind it effectively.
Primocon is a good basic underwater primer so the scheme you plan is fine but without the etch primer. I think it best to assume the surveyor was "confused" when he suggested that. If you decide to use a rust convertor, and this is one time when it just might be suitable, make sure you remove any residue thoroughly before the first coat of Primocon.
As with most conventional underwater primers there is no substitute for film thickness so make sure you follow the instructions as to number of coats. I would put at least 2 coats on before filling then build the rest up over the filler.

 

[Amp1ng]

Thanks all for the helpful advice.

Since posting I had given it some more thought myself and in line with the last reply I had considered using POR 13 on the bare steel, then filling then a coat of primocon then antifouling?

Does this make anyone gasp in horror?

 

[Rigger Mortice]

.Primocon is a good basic underwater primer.

Yes, but is it any good as a primer for Epoxy? I thought it was meant for Antifouling.
If Epoxy isn't compatible with Primocon then it will cause problems.

 

[vyv_cox]

Thanks all for the helpful advice.

Since posting I had given it some more thought myself and in line with the last reply I had considered using POR 13 on the bare steel, then filling then a coat of primocon then antifouling?

Does this make anyone gasp in horror?

My keel was gritblasted, primed with five or six coats of West epoxy, then Coppercoated. During the following season we sailed over an almost invisible fishing float comprising some blocks of polystyrene tied together with wire. The result was a deep gouge along the keel, down to bare metal.

In the following spring I ground out the area, primed immediately with West, followed up with another four or five coats of the same, each one applied to the previous one tacky. Then three or four coats of Coppercoat. After one season since then the repair is looking fine.

 

[Pasarell]

Keel repair

Yes, but is it any good as a primer for Epoxy? I thought it was meant for Antifouling.
If Epoxy isn't compatible with Primocon then it will cause problems.

You can use a ready made filler such as Watertite over Primocon without compatibility problems. This doesn't make Primocon compatible with solvent based epoxies.

To the OP. Your scheme is OK but make sure you get enough coats of Primocon on. When you say "a coat" I'm not sure if you mean 1 coat, but if you do then you might as well not bother. Several are required to make it really waterproof.

 

[jakeroyd]

I have posted here recently about a rusty keel , similar to this thread in some ways.
A search brought up vactan (available on Ebay , quite cheaply)
I plan to grind off , apply vactan , then epoxy tar like International VC 2 , then antifouling.
Prior to this I filled in my rust holes with epoxy putty , this was before I had tried a rust converter. If this falls out when I sand it I will vactan it and try agian with epoxy putty or epoxy tar.

 

[ianj99]

To stop rust the first coat should be zinc rich epoxy.

Which is available from http://rust.co.uk

I use their Epoxy Mastic & their 93% zinc epoxy on my steel ketch.

The term mastic is a bit of a misnomer as its brushable, with excellent filling ability.
I plan to spray the hard to reach interior surfaces with mil spec dintrol from the same supplier. Its clear (and non sticky when dry) so regular inspections are possible.
I