Re: [PSUBS-MAILIST] Hot-galvanize stainless steel ?

[Lew Clayman <lew_clayman@yahoo.com>]

A surface boat trick you might consider is to sacrifice zinc blocks by mounting
them on the hull, near metal which might corrode.  The zinc corrodes instead,
so you replace it every so often (every year, every few dives, depends on how
big the zincs are, conditions in the water, local metals, etc).  

If you have an electically conductive environment (salt water!) and more than
one kind of metal, then the electrons WILL migrate, the current WILL flow, and
something will corrode.  The zinc protects the ship by oxidizing instead of the
ship.

-Lew

--- Carsten Standfuß <MerlinSub@t-online.de> wrote:
> Alec - during diving in the baltic I found the wreck of a 
> modern sailboat maybe just 2 years underwater. 
> I salvage a rigging terminal made from unpainted stainless steel. 
> It has very bad big corrosion holes in many parts.. 
> 
> Is there a material I can put between the both - key and hole 
> which is : 
> - not metal 
> - can be loaded with the weight pressure of the keel 
>   (load area is 3600 mm2 with a load of 3 N/mm2) 
> - is just 1-2 mm in tickness ? 
> 
> see you - Carsten
> 
> Alec Smyth schrieb:
> > 
> > Carsten, maybe I'm misunderstanding it, but as I understand your
> description
> > you would have:
> > 
> > - A stainless shaft (or "key")
> > - A stainless insert for it welded into a dropweight of plain steel
> > 
> > If you galvanize the drop weight (with the insert already welded of course)
> > then the key and the key-hole would be of different metals so the corrosion
> > problem would be worse than if they were both just SS. Wouldn't it be
> enough
> > to just paint the drop weight like the rest of the sub for corrosion
> > protection purposes, but leave the key-hole unpainted? If you wanted to get
> > really fancy, you could sleeve the shaft in plastic like nylon or teflon,
> to
> > prevent it from sticking after a year in the water.
> > 
> > rgds,
> > 
> > - Alec
> > 
> > -----Original Message-----
> > From: MerlinSub@t-online.de [mailto:MerlinSub@t-online.de]
> > Sent: Thursday, January 24, 2002 11:49 AM
> > To: personal_submersibles@psubs.org
> > Subject: Re: [PSUBS-MAILIST] Hot-galvanize stainless steel ?
> > 
> > "Dan H." schrieb:
> > >
> > > Carsten,
> > >
> > > Why not just weld in a stainless steel plate with your key way already
> > > in it into a hole cut in your steel weights.  Instead of cutting out the
> > > key in the actual steel weight, weld in a piece of stainless for the key
> > > to fit into.
> > 
> > That it exact was I want to do. Maybe my description was a little short.
> > 
> > > Even if you had the whole thing galvanized and it didn't
> > > take well to the stainless it wouldn't matter.  Actually, the part of
> > > the key way in contact with the key will probably wear through the
> > > galvanize in time anyway just from rocking back and forth in use, won't
> > > it?
> > 
> > That is exact the question - would the galvanize hold on the stainless
> > - or not ? I think that if the zinc gives way from the key-hole - we
> > have a direkt contact from two parts of Stainless steel with a very
> > little
> > gap filled with saltwater between them - all the time in seawater -
> > maybe
> > the hole year. That should generate maybe a corrosion problem - and if
> > one of the key-hole surface has to much structure on it - the key will
> > not turn.
> > 
> > Maybe it would be better to make the key-hole-plate  from normal
> > carbon steel. I am not affraid that the zinc gives way during
> > "Using the key". If I use it - the drop weights gives way and the
> > sub is not longer able to dive - so the weight will be lost and will not
> > repaint..
> > 
> > >
> > > Just a question; why didn't you use lead for your drop weight?  There's
> > > so much more weight for the area it takes up.  A ton of old tire weights
> > > doesn't make that big of a pile.
> > >
> > Maybe I will do it - a drop weight build from 1/3 inch strong steel
> > plates
> > as a box - and than filled with lead. It will be depents on the final
> > weight calclulation - some month before CSSX contact the water in our
> > river.
> > 
> > Carsten
> > 
> > > Dan H.
> > >
> > > Carsten Standfuß wrote:
> > >
> > > > Hi submadmans and ironheads,
> > > >
> > > > One question about metalurgy :
> > > >
> > > > Is it possible to Hot-galvanize stainless steel ?
> > > >
> > > > I want to build the drop-weights from normal mild
> > > > and cheap steel and hot-galvanize it.
> > > > The release-key will be made from stainless steel (SS).
> > > >
> > > > For the reason that the welded key-hole inside the
> > > > dropweight can be made easy from the same plate as
> > > > the key and with the same waterjet cut - I ask this
> > > > unuseual question.
> > > >
> > > > drawing without scale : (and below 40 KB :-) )
> > > >
> > > > I = Stainless steel release key
> > > > O = Stainless s. hot galv.? key hole
> > > > = = mild steel hot galv.drop weight
> > > >
> > > > _____________________________________
> > > >
> > > >                  IIIIIIIturn90°
> > > >                  I
> > > >     =========    I    ========
> > > >    ==========OOO I OOO==========
> > > >   ===========  IIIII  ===========
> > > >
> > > > _________________________CS-1/2002___
> > > >
> > > > And please - I know that a full SS drop weight will fit
> > > > the problem.. .. but I have three weights of 1,3 ts -
> > > > means it generate another one..
> > > >
> > > > regards - Carsten


=====
"In baseball, you don't know nothin'."
             - Yogi Berra
=====

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