Priming underwater steel

[bob26]

I am about to strip off and recoat my steel bilge plates and rudder.

I wonder if anyone has useful experience on the best primer for underwater steel? I use International Cruiser antifouling (out of habit mainly) and International's advice was to coat bare metal with Primocon before antifouling. It's what I've always done but it never served me particularly well in the past.

I wonder if some sort of epoxy primer might be better?

 

[Bosun Higgs]

Big steel structures are primed with epoxy though I have heard that ships bottoms are often coated with chlorinated rubber. Tried both on the bilge keels of my old Hunter and the chlorinated rubber one lasted best

 

[electrosys]

If you're taking the fins back to bare metal, then it might be worth considering applying Zinga for protection. http://www.zinga-uk.com/
But I don't know about subsequent coats for anti-fouling. Their website has an enquiry facility - so might be worth asking them for advice ?

I have used zinc phosphate primer (the colour of red oxide - confusing, or what ?) from Leigh's Paints - as used on bridges etc - excellent stuff, as thick as cream, takes any type of top coat. They normally only supply direct to industry, but will supply to an individual end-user on request (but it ain't cheap).

 

[coreng]

Replace Primocon by Interprotect. Avoid mixing paintsystems to keep surprises out...

 

[Conachair]

This is the best stuff I've come across.

http://ppgamercoatau.ppgpmc.com/docs/products/Amerlock Sealer0906.pdf

 

[pentagram]

zinc phosphate primer is very good. ive used it for years

 

[idpnd]

Just to second conachairs vote, (thanks for the recommendation by the way) I got it from PPG Blegium direct, quite affordable. Apparently its what they use on old bridges and oil rigs that arent sandblasted etc.

 

[bob26]

Thanks

Thanks for all these helpful replies.

I'm looking into the compatibility with antifouling of some of these things.

Some suggest a tie coat...for which International suggest Primocon for Cruiser over unknown substrate...so may be putting that on anyway!

 

[xtiffer]

Replace Primocon by Interprotect. Avoid mixing paintsystems to keep surprises out...

Isn't Primocon made by International?
Having said that I would epoxy prime it first.
Cheers,
Chris

 

[nickd]

For the last two years I have used primocon at vast expense and am not delirious about the results at all. Just looked at the keels this weekend and I do not think they could be much worse if I had applied poster paint! I thought that this year I might try hammerite on the basis that its cheap, it might work, but as I'm on a drying mooring I will be able to see if it fails early.

 

[vyv_cox]

It comes down to what you want to spend and how long you expect the treatment to last. I had my keel gritblasted and epoxy coated and it lasted ten years. Previous to that I wire brushed it and painted with Primocon and other non-epoxy products and two years later I was doing it again. My view is that epoxy throughout is vastly preferable but unless the quality of the preparation is as good it's unlikely to be totally satisfactory.

I've never used it but the product recommended by Conachair looks pretty good, similar to coatings used on offshore platforms.

 

[ianj99]

For the last two years I have used primocon at vast expense and am not delirious about the results at all. Just looked at the keels this weekend and I do not think they could be much worse if I had applied poster paint! I thought that this year I might try hammerite on the basis that its cheap, it might work, but as I'm on a drying mooring I will be able to see if it fails early.

Try 93% zinc epoxy from:

http://rust.co.uk

I haven't tried it yet, but have some ready to apply to my steel hull.

I am using / have used their Epoxy Mastic on the topsides and it is extremely effective. Its very viscous but brushable - gives high build and easily sanded.

Did a test on some rusty bits a year ago where the toe rails meet the deck and even without any overcoating (UV protection), it did the job.

I

 

[ghostlymoron]

For the last two years I have used primocon at vast expense and am not delirious about the results at all. Just looked at the keels this weekend and I do not think they could be much worse if I had applied poster paint! I thought that this year I might try hammerite on the basis that its cheap, it might work, but as I'm on a drying mooring I will be able to see if it fails early.

I tried Hammerite primer No 2 a couple of years ago. As you say it's cheap but wasn't very effective although I did only prepare by hand wirebrushing. It might have been better if I'd use a cup brush on an angle grinder.

 

[Dipper]

I successfully 'painted' a steel rudder on a Hurley 22 with several coats of the very cheap (rubbery) car body underseal. It's supposed to self seal when penetrated. I had the boat about 7 years. I recoated it once but it didn't really need it. There were just a couple of small patches with rust showing through.