Re: [PSUBS-MAILIST] Interior paint (was: Scuttle valve)

I don't know. I believe this method is used to bond the coating better. Other than zinc anodes. I have seen steel hulled vessels with an electronic device on board, that works along the lines of reverse polarity.

To create corrosion is the same as making a battery. I believe the theory has to do with altering or stopping electron flow. Electron flow from the cathode to the anode causes the corrosion and creates voltage.

Some U.S. Navy ships i have worked on use this effectivly, and have no zincs at all. I don't know the cost.

bob

Steven Mills <cirtemoeg@juno.com> wrote:

Bob,

Taking electricity [ andodes/cathodes etc. ] in a different direction.
Would electrostatic bonding of the coating to metal be a good
solution. It would assure any pores in the metal would get covered
or sealed. Or is this overkill [ and probably expensive? ].

--Steve

On Mon, 8 Mar 2004 16:44:51 -0800 (PST) Bob Duncan
writes:
> 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 normal 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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