Re: [PSUBS-MAILIST] Ambient vs. 1 ATM: the historical perspective

["Captain Nemo" <vulcania@interpac.net>]

----- Original Message -----
From: <VBra676539@aol.com>
To: <personal_submersibles@psubs.org>

" Speaking of ballast tanks, I've got a question.  I take it you have to get
INTO ballast tanks occasionally to clean them out (either "crud" or
corrosion).  How do you do this?

I think Vance pretty much nailed it.  I used to wash the entire sub, inside
and out, with fresh water after use.  I'd flood the tanks and drain them
repeatedly.  The last time I'd add a product that is designed to retard rust
in tanks by depositing a "waxy finish" on the metal as the water drains
away.  Then I'd let 'em dry out really well, and close all the valves in the
belief that limiting the amount of oxygen inside the tank would inhibit
oxidation.  (Of course, I always had to keep the sub parked in the garage,
out of the sun, to keep heat expansion from putting adverse pressures on the
system.  Not that it couldn't withstand it, but why endure stress when you
don't have to?)

I've had the sub going on ten years now, and as far as I can tell, there's
no appreciable corrosion inside my tanks.  But I am coping with exterior
rust.  A volcanic island is a pretty corrosive environment.  My plan (while
finishing the exterior scale detailing) is to treat and coat every exposed
metal surface before dunking her in salt water.  Right now, I'm mechanically
stripping minor surface rust; treating surfaces with chemical rust
inhibitor-converters; and then I'm going to coat everything with fiberglass
resin.  I'm thinking about how I can do this with the inside of the tanks,
too.  I'm thinking about a chemical-etch; converter / inhibitor; and then
sloshing finishing resin around inside by "rocking the boat" on a roller
cradle.  All this might not even be necessary, but I'm going to do it
anyway.

Vance's point about stainless tanks is a good one; it's more expensive than
mild steel, but in the long run well worth it, I think.

VBR,

Pat