can a unopened can of anti fouling paint last 10 years

[Mannyslv]

i was debating with a friend of mine weather or not a can of antifouling paint can last 10 years if it has never been open.

if you flip the can every 3 months lets say, will that help the copper not get stuck together.

would apreciate any comments about this subject
thanks

[Jon Hacking]

Manny, I don't know, but I wouldn't try.

When we crossed the Atlantic from Cape Town in '81, a 1 year old can of antifouling rusted through and leaked into the bilge. We didn't notice at first, but we did notice that Margi didn't come up for her watch. No problem, she was asleep and there were lots of folks on deck so we stood her watch for her. But then we smelled the paint fumes and realized that we couldn't wake her up. So we carried her up on deck for some fresh air and looked after her as best we could. She eventually woke up about 24 hours later, and seemed fine. But a few years later she developed brain cancer and died, while still in her 20s. I don't know if the events are related, but we now don't carry many old paint cans...

[danielamartindm]

Cans of paint in my garage, absent a marine environment, seem to rust up pretty quickly. I know the stuff is expensive, but I'd be more worried about a leak into the bilge than the effectiveness of the paint after years of storage.

[JPA Cate]

Originally Posted by Jon Hacking

Manny, I don't know, but I wouldn't try.

When we crossed the Atlantic from Cape Town in '81, a 1 year old can of antifouling rusted through and leaked into the bilge. We didn't notice at first, but we did notice that Margi didn't come up for her watch. No problem, she was asleep and there were lots of folks on deck so we stood her watch for her. But then we smelled the paint fumes and realized that we couldn't wake her up. So we carried her up on deck for some fresh air and looked after her as best we could. She eventually woke up about 24 hours later, and seemed fine. But a few years later she developed brain cancer and died, while still in her 20s. I don't know if the events are related, but we now don't carry many old paint cans...

@Jon,
What a sad story, and what a profound caution!

As to bottom paint, if you've come across some very old stuff, contact the manufacturer. Formulatins have changed a lot over the years, and it will take a paint specialist to give you an accurate answer, and even they, may have differing opinions.

Ann

[mike d.]

I don't believe the paint would go bad ! The problem is to get the copper back in suspension, without opening ! It would have to go into 1 of those paint store shakers to get it back in suspension! If you store it in the bilge wrap it in multiple layers of plastic bag, to seal it from the salt environment. Then secure it from movement so the bags can't get punctured! I don't know if this is accurate, with the new water based paint !
I have bottom paint from the 70s I still use ! It just takes a long time to get it mixed again!

[Island Time O25]

A few years back HM store in Portland had a big anti-foul paint sale during March Portland Boatbuilders' Show weekend. I got 3 cans as they were something like 50% off reg. price. Used one can later that May and put away the other two. I had a 27 footer at the time. Then I forgot all about these 2 cans and next 2 or 3 seasons kept buying new bottom paint. Then I remembered that I had those two cans stored in a shed in non-marine environment. Since I already had a 36 footer by then, one can was not enough so I used about 1/3 of the 2nd can. I don't do more than one good coat as my season is only 5 months. So the next year I used the rest of that 2nd rediscovered can. All in all this last can must have been years away from its date of manufacture with no ill effects on its effectiveness.

Perhaps in a wet marine environment the electrolysis eats its way through. But in dry and non marine storage I do not believe that it would degrade to the point of fully losing its effectiveness. May be degrades somewhat but at $200-300+ per can I would definitely not throw one away.

[Island Time O25]

Originally Posted by mike d.

I don't believe the paint would go bad ! The problem is to get the copper back in suspension, without opening ! It would have to go into 1 of those paint store shakers to get it back in suspension! If you store it in the bilge wrap it in multiple layers of plastic bag, to seal it from the salt environment. Then secure it from movement so the bags can't get punctured! I don't know if this is accurate, with the new water based paint !
I have bottom paint from the 70s I still use ! It just takes a long time to get it mixed again!

I used the old "stirrer stick on electric drill" method. Punctured a hole in the can lid, inserted the swirling attachment through the hole into the drill, closed the lid tightly and stirred for about 20 minutes, may be longer. It still was less time consuming then driving to the hardware store and back.

[BlackHeron]

Will any paint last that long? If the can doesn't rust out and fail, maybe. I'd talk to the manufacturer about their recommended storage intervals. It might be different for hard or ablative paints. What bottom paint lasts 10 years anyhow so that you'd be waiting that long to re-apply anyhow? Worried about changing rules and availability of effective paints 10 years down the road? That's a legitimate concern I would imagine.

I was more worried about changes in future paints not being compatible with current paints when I started fresh with our own bottom job from gelcoat back up. it was a real PITA to take it all down, fix all the pits and apply the many coats of interlux interprotect epoxy. I wanted whatever I put on the new anti-moisture barrier to compatible with any new paints that will be available in the future next time. I went with Pettit Ultima SR-60 because it was the best stuff I could find, and after talking to a number of representatives who assured me that I'd be able to find effective bottom coats 10+ years into the future that would be compatible to paint over it.

[Eder]

I used some Petit Horizons that was opened 3 years ago the other week at my haul out...it was fine, I had it wrapped in a couple garbage bags and stored on the boat. I'll use it again for touch up next year hopefully.

[Island Time O25]

I'm more inclined to trust the advice of the end users based on their actual experiences than of a customer rep who is in the business to sell new paint - the more the better.

As long as the copper suspension did not clump up I don't see a down side of using properly stored old bottom paint. And others say the same thing.

[Eder]

The boat tends to keep it stirred.

[sailor1924]

Back in the day a buddy and I bought some buckets of navy surplus paint. It was 10 years old when we got it and my friend used some seven yen years later. It was fine after 17 years.

[thinwater]

I've used paint that old several times. Someone gave me an old 5-gallon bucket. Lasted 2-years each time.

You have to mix it a lot, of course.

[Jspla]

I had a similar situation, where I purchased 2 extra cans of West Marine ablative paint and completely forgot about them for 2 years. They were stored in my basement and the cans looked like new. It took about 40 minutes to completely suspend the copper. Used these cans forn3 additional seasons doing ups. The final paintbwas used on the 6th year post purchase

[senormechanico]

Originally Posted by Eder

The boat tends to keep it stirred.

Sailing back and forth from the Northern to the Southern Hemispheres?
I'd think it would be easier just to occasionally invert the cans!

( like what I just did with my Trinidad SR with Irgarol to be applied in April )