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Some prior emails from last year's thread were missed. Below are two
from Vance and Alec that are very significant.
-Jim
From: vbra676539@aol.com
Reply-to: personal_submersibles@psubs.org
To:
personal_submersibles@psubs.org
Sent: 3/21/2011 9:46:58 A.M. Central
Daylight Time
Subj: Re: [PSUBS-MAILIST] Paint.....Cheap or
Proper?
Jim and all,
I agree about the use of best available coatings. On the exterior of
Gamma and my K-350, I use a zinc coat on bare steel, hi-build epoxy over that
as a strenghtening component and tie coat, and then polyurethane over that as
the final coat. The polyurethane is able to take a harder whack without
fracturing and doesn't chalk in the Florida sun. The combination is getting on
toward bulletproof.
If you want to do it up really well, there are Dimetcote vinyls
available. Those are milspec Navy coatings. Expensive. $600+ per gallon,
but it is really good stuff, as you might imagine. We used it by the truckload
at Perry. But paint technology has advanced since then, so I don't know what
the very best is these days.
There are less expensive and labor intensive methods for the interior,
however. Gamma's ABS specs for interior coatings call for Rustoleum over zinc,
and that works very well. Nine years in storage and the coating only has a
very few pinhole issues to show for it. That isn't a guess. I'm looking at it
right now.
The zinc undercoat is critical. After that, you want something that
seals. That sounds patently obvious, but keep in mind that this stuff is
slathered onto a pressure vessel that flexes under pressure, and works in a
hostile environment. You skimp on it at your peril.
Vance
-----Original
Message----- From: JimToddPsub <JimToddPsub@aol.com> To:
personal_submersibles <personal_submersibles@psubs.org> Sent: Mon,
Mar 21, 2011 10:30 am Subject: Re: [PSUBS-MAILIST] Paint.....Cheap or
Proper?
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.
Jim
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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Hi All,
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.
What do you think?
Thanks
James
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