GL: Fwd: Great-Loop Digest, Vol 50, Issue 6

[Rex Miller]

---------- Forwarded message ----------
From: Rex Miller <rexwmiller@gmail.com>
Date: Feb 7, 2007 12:23 PM
Subject: Re: Great-Loop Digest, Vol 50, Issue 6
To: great-loop@lists.samurai.com

All Stainless Steel is able to rust.  Stainless Steel remains passive as
long as fresh oxygenated water washes over it.  As soon as the water against
the metal becomes de-oxygenated the metal will become active, as no more
chromium ions can be attracted to the surface of the metal by the free
oxygen dissloved in the water, then the steel component will begin to rust
in the normal way creating red Ferric Oxide Fe2O3.  Prime locations for
corrosion are at through hull fittings where the core can become saturated
and with little flow the trapped water becomes de-oxygenated beginning the
crevese corrosion process.  If caulking has been cut out, causing scoring of
the Stainless Steel surface, a stress riser has been created and accelerates
the deterioration.  When cleaning Stainless Steel the problem is that all
the Fe2O3 has to be removed, and ideally, the surface re-polished.  Rough
surfaces and scratches are ideal starting locations for rusting to begin.
Chemical etching materials have to be completely removed or neutralized or
they will cause renewed rust.
Never seal the inboard side of a through hull fitting or water can become
trapped and troubles start.


-- 
Rex W. Miller SA(r)
Telrex Marine Services