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Bob,
Thanks for the info. I gather as long as the
anodes are contacting the hull electrically and in the water, they will
work. Maybe the placement isn't all that critical.
It would seem that the size of them would be
important though. If there was to much anode for the hull current would
probably flow the other way and be just as destructive. A balance is
what's desired, right? I'm just guessing.
Can anyone else contribute here?
Thanks, Dan H.
----- Original Message -----
Sent: Tuesday, March 09, 2004 12:08
PM
Subject: Re: [PSUBS-MAILIST] Interior
paint
Hello,
I would have to look thru some books for placement. Usually on a
surface vessel the zincs are placed a little below the water line.
Large vessels i have worked on (Navy aircraft carriers) have the
hull zincs about 6 ft (2 meters) below the waterline, the hull draws about 35
feet of seawater. Smaller steel yachts that draw about a meter or less of
seawater will have them a foot or less below the water line. I would have to
look at large military submarines, i believe they are set up for what the
water line would normaly be when running on the surface. I may be wrong here.
I've never changed zincs on a submarine.
There is a formula, which i don't know, because i haven't used it.
That tells the amount of zinc to use. Some people say if you have too much
anode material it can cause damage. Usually it is better to err on the little
too much side.
Trim planes and hydrofoils need to have their own.
One thing about using zinc (the most common) anode material
is that it melts easily (below 1000 deg. F.) which means they can be recast to
about any shape you want. Which makes it easier to make them a shape that is
streamlined. Causing less drag on the vessel.
Bob
"Dan H." <jmachine@adelphia.net>
wrote:
Carl,
No
doubt there will be some electrical emissions from my sub. Some
from
electrolytic action and some from equipment inside. All my
electrical
systems, except leak detection, has it's own power return
circuit, above
ground. It does not connect to the hull at all. The leak
detection circuit
has so little current flow when dry that it shouldn't
be a factor. I doubt
a freshly painted sub mini will have much more of an
electrical field then
the big hull's that are sunk all along the
coast.
Actually, attracting fish would be pretty interesting, as long
as their
jaws don't open over six feet and their not hungry for yellow
painted steel.
;-)
Dan H.
----- Original Message -----
From:
"Coalbunny"
To:
Sent: Monday, March 08, 2004 9:52
PM
Subject: Re: [PSUBS-MAILIST] Interio! r paint
> I'd be
concerned with emitting any electricity from the craft as
>
electricity attracts fish. Unless you want to go fishing, that is.
>
Carl
>
>
> Dan H. wrote:
>
> > Bob,
>
>
> > You seem to know what your talking about when it comes to
corrosion.
> >
> > I've seen anodes on some out boards and
understand the principle but
> > don't really have a handle on what
I need.
> >
> > My K-350 will be ready for launch soon so
it's time for me to get the
> > anodes I need. I have a painted
carbon steel hull with several pieces
> > of stainless steel
mounted to it, two aluminum props and one bronze
> > prop. A real
pea soup when it comes to corrosion. Most of the time I'll
> > be
diving in fresh water but sometimes sea water. I doubt it will stay
>
> in the water for more then a day or two at a time.
> >
>
> If your familiar with the K-350 design and size, can you give me an
idea
> > of the size anodes I need and where to best place
them?
> >
> > Thanks, Dan H.
> >
> >
----- Original Message -----
> > From: Bob Duncan
> > To:
personal_submersibles@psubs.org
> >
> > Sent: Monday, March
08, 2004 7:44 PM
> > Subject: Re: [PSUBS-MAILIST] Interior paint
(was: Scuttle valve)
> >
> > To add to my last e-mail. I
would like to talk a little about
> > corrosion and corrosion
control. Which is usually the primary
> > purpose of a coating
system (corrosion control). It takes 4 things
> > to make
corrosion: An Anode, a Cathode, a metal path, and an
> >
electrolyte. Oxygen is the primary electrolyte. Oxygen is contained
>
> in water, and of course a norma! l atmosphere. The salt in sea
air
> > (not only sea water) is a strong electrolyte.
> >
The easiest and most common method of corrosion control is to put a
>
> barricade on the metal surfaces to prevent the electrolyte from
>
> contacting the metals (anode and cathode). Since any structural
>
> metal is an alloy ie: steel is an alloy of Iron and Carbon you
>
> alread have an anode and cathode in contact with each other. We
>
> can't prevent this.
> > There are charts available in
corrosion control manuals, or
> > corrosion engineer manuals that
list how far apart metals are from
> > being the cathode or the
anode. The anode gives up electrons or is
> > the one to rust away
(if you don't mind these terms "rust") We put
> > zinc anodes on
steel ships to save the steel. The zinc anode is
> > eaten away
instead of the steel, then as a rule of thumb, the zinc
> ! > anode
is replace when it is half gone.
> > Anytime you put a metal
fastener thru metal, you again create a
> > corrosion problem. As
the fastener is seldom the same alloy as the
> > material it is
holding together.
> > I'll try to keep this short, and simple
!!!
> > When you add electricity to the system, you have more
electron
> > flow, and increase you potential for a corrosion
problem. It's very
> > difficult to keep electricity out of a
modern boat!
> >
> > Once all the metal is welded it is
probably (possibly depending
> > on the situation and design) the
best time to clean the surface.
> > Apply a chemical conversion if
you are going to, prime the surface
> > and apply a top coat. Then
add the systems. It is very important to
> > coat all metals used
in the marine industry. There are few
> > exceptions, one being
that when you use an anode (such ! as zinc on
> > steel) that the
contact surface be bare. As it wouldn't do much good
> > to put the
zinc on a painted (or coated) steel surface.
> >
> >
Corrosion control is an ongoing war in the marine industry.
>
>
> > Bob
> >
> >
> >
> >
Bob Duncan wrote:
> >
> >
Hello,
> > I would think that if it is an ambient pressure
submarine,
> > that you should be able to use the same kind of
coating that is
> > used in hyperbaric chambers.
> > For a
1ATM submarine, i would use epoxy or polyurethane primer
> > and
topcoat. We dont' use the word paint, because paint is a
> >
decorative, and these are a coating system. I'm sure you will
> >
have a fair amount of condensation, on the inside of the boat.
>
>
> > bob
> >
> > Michael B Holt
wrote:
> >
> > On Mon, 8 Mar 2004 15:05:26
-0800 Steven Mills writes:
> > >
> > >I had not
thought of water-proofing the interior, but it
> > makes
sense.
> > >Paint or plastic? Would there be residual
out-gassing over
> > time from
> > >the plastic if one
used spray-on vinyl like used in beds
> > of pick-up
> >
>trucks?
> > >What would be the curing time of paint versus
plastic?
> >
> > Hey, let's talk about this. What sort of
paint can be used
> > safely on the interior of any sealed cabin?
Some paints
> > have an odor that lasts for a long time.
>
>
> >
> >
> > Mike
> >
>
>
> >
>
>
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> > Dun! can
>
>
>
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Duncan
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