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

[Steven Mills <cirtemoeg@juno.com>]

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
<katsurencho@yahoo.com> 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 <katsurencho@yahoo.com> 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 <tlohm@juno.com> 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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> Duncan
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> Fact is stranger than fiction. Truth is stronger than fact. R. 
> Duncan
> 
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