Immersion is a long-term consideration, a category we don't fall into. UV
really isn't a large concern for us in Florida, either, as most of the subs
I know about are stored indoors or at least under cover, and a few hours
exposure doesn't seem to do much harm. That said, any boat owner you care to
check with down here will tell you that epoxy SUCKS as a long term outer
coating. It simply will not put up with years of exposure. That doesn't make
polyurethane easier. In fact, it gets harder, as you have to abrade the cured
epoxy tie-coat to ensure a good mechanical bond between it and the
polyurethane top coat.
Jim, I'm sure your guys know their coatings. However, they are misinformed
as to overall serviceability. If you beat up the epoxy, then you get zinc
exposed at best, and your bare hull at worst. Nine times out of ten, if you
scuff the polyurethane, the epoxy underneath will survive and protect you until
you can get your paint brush out again. Each component provides additional
protection, something to be considered over time.
That said, the new coatings available today are so superior to the old days
that you can use just about anything and, with care, do pretty well. We spend
more time on the trailer than we do in the water, so if you pay attention, then
almost anything you use will provide adequate protection. Except for Alex, of
course. He invented a rust maker. Love to see that.
Vance
-----Original
Message-----
From: kocpnt tds.net <kocpnt@tds.net>
To:
personal_submersibles <personal_submersibles@psubs.org>
Sent: Mon, Mar
21, 2011 2:30 pm
Subject: Re: [PSUBS-MAILIST] Paint.....Cheap or
Proper?
Hi Jim,
I'm not sure of the correct answer! I know that it's done and do not know
details, however my paint reps were emphatic. I live in Wisconsin and UV is a
much smaller concern than for Vance etc. so I just used the epoxy.
I would reccomend talking to a knowledgable rep before purchasing.
Best regards,
Jim K
On Mon, Mar 21, 2011 at 1:13 PM,
<jimtoddpsub@aol.com> wrote:
Jim
K,
Thanks much. Regarding polyurethanes, is there a distinction between
a few hours of immersion (2-10) for a small sub versus much longer in the case
of a larger sub, boat bottom, or underwater structure?
Jim T
Sent on the Sprint® Now Network from my BlackBerry®
Date: Mon, 21 Mar 2011 12:54:03 -0500
Subject: Re: [PSUBS-MAILIST] Paint.....Cheap or Proper?
Hi all,
My two cents!
While there some exceptions, (most notebly moisture cure urethanes) epoxy
is almost always the prefered product for corosion protection especially in
immerssion situations. Corrosion protection is largely a function of mill
thickness and heavy epoxy mastics can be applied at 5 - 10 mils DFT dry film
thickness per coat. Most polyurethanes can not be applied over 5 mils. The
rust inhibitive properties are very good with Sherwin-Williams Macropoxy 646
and two full coats will easily cover the blast profile of about 4 mils that
you will probably end up with. If you want great shine topcoating with
polyurethane is good. I know phil does this, however my tech reps tell me that
polyurethanes do not perform well in immersion situations.
Best Regards,
Jim K
Kocourek Industrial Painting
On Mon, Mar 21, 2011 at 10:02 AM, Stewart Gardiner
<stew@terminalsolutions.biz>
wrote:
Thanks
for clarifying that Jim! I did mean 2 part polyurethane…. Epoxy being a
generic term for anything using a hardener etc J the particular paint brand ive used
on fibreglass boats before is Norglass or Norcoat..
The
polyurethane primer came out so well I was actually contemplating leaving it
in primer and not worrying about the top coat! J but UV protection might not be so
good with the primer…also its slightly porous…
The last
time I worked extensively with coatings was 1983. We were using
two-part polyurethanes that cost $250 USD per gallon at that
time. Epoxies were considered older technologies that were
becoming obsolete, however I think the term "epoxy" is being used
generically to denote any type of two-part coating (color and catalyst or
hardener).
This is one
of the last places I would try to save money, and I would spend just as much
on interior primers and coatings as exterior for two
reasons:
1.
Preventing corrosion is a lot better than trying to cure it, and having to
do that (and redo) the inside the sub can be a bear.
2.
After an operation, I can wash down the exterior with fresh water and
whatever else I chose to use. That's not an option with the
interior.
I've also
wondered about spraying the entire exterior with a wax several hours prior
to a mission but haven't investigated that. Seems
reasonable.
The first
time I sandblasted and painted Snoopy, I put lots of coats of
expensive epoxy on the outside, but had this same exact thought about the
inside. That surely won't get wet, therefore cheap and
ordinary paint should do! Well, when Snoopy was in Florida the
humidity was 100%, the temperature was something ridiculous, and
climbing in and out even splashed a little salt water inside. With the
combination of those three factors, when I was being towed out to a dive
site the inside rusted so fast I could actually see the rust move. I mean
that literally, you could see it popping up from under the
paint, rather like a paper towel that has been laid over a counter
that's sprinkled with water.
I still
don't use as expensive a paint on the inside as the outside, but one
paint I've found is economical yet tough is a two part epoxy for
painting garage floors. It's very thick, giving really good coverage,
and resistant to abrasion. The downside is there aren't
any rust preventers in it because it's intended for concrete, so
you want to spray a base for metals underneath.
Best,
Alec
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it.
Im going
to paint the inside of my battery pods today. As theoretically, the
insides should not get wet, i was thinking of using just a normal metal
paint like Hammerite or something. A straight forward paint that you
would use to paint outdoor railings and things with. Do you think
this will be ok or should i go for the "proper" 2 part epoxy marine
primer? Its just really expensive.