Date:         Thu, 22 Apr 2010 07:46:37 -0700
Reply-To:     Don Hanson <dhanson928@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Don Hanson <dhanson928@GMAIL.COM>
Subject:      Re: Hose clamps..
In-Reply-To:  <037701cae1ec$2bdfd020$839f7060$@net>
Content-Type: text/plain; charset=ISO-8859-1

  I know nothing of the Chemistry but I do have plenty of practical exposure
to SS.  Working with yachts in a full service yard for a few years.  Very
very rarely did we encounter hose clamps with 'rusted' screws.
  We fabricated many custom Stainless steel rigging and hardware pieces
right in house...welding them with MIG.  Quite an art, welding SS in an
attractive manner.  We did lots of fabricating,  turning the parts on the
lathe, cutting them from sheets on the band saw.   Many yachts have a
surprising number of custom fittings, unique and made just for that one
boat...Often these parts were made from SS.   I never encountered one with
real rust, though some did show a very very light discoloration that looked
like it could rust...sometime in the next thousand years or so..
.A majority of sailboats use SS 'wires' for the rigging..Stuff that is in
constant motion, under stress, sitting immersed in salt water.  Even in that
application, SS does not degrade very quickly...Perhaps the pieces that were
welded improperly were 'Long-Gone', rusted away...that is why they never
showed up in boatyard experience, but..
  I would imagine any hose clamp manufacturer who sold his wares to the
marine industry would not stay in business very long if he sold clamps that
rusted out...I'd opine that if you find a welded hose clamp for sale to
marine customers,  it will  have been "Properly" welded so that it's
corrosion resistance has not been compromised...
  An aside:  Standard practice on boats is to put two hose clamps on every
thru-hull fitting.

  Don Hanson

On Thu, Apr 22, 2010 at 12:19 AM, Tom Hargrave <thargrav@hiwaay.net> wrote:

> Stainless is made corrosion resistant by a thin oxidation layer on the
> surface of the metal called passivation. Spot welding will destroy the
> oxide
> layer protecting the SS from rust but it takes very little time, literally
> seconds, for the weld area to re-passivate and protect the welded area from
> corrosion.
>
> The real issue is not "is the clamp spot welded", but what series stainless
> steel is it made from? Good stainless steel clamps should be made of 304
> series stainless steel.
>
> From http://www.ssina.com/faq/index.html#6 web site:
> "When the amount of chromium (in an iron matrix) exceeds 10 ½%, a complex
> chrome oxide forms instantaneously that prevents the further diffusion of
> oxygen into the surface and results in the "passive" nature of stainless
> steel and its resistance to oxidation (or corrosion). A chemical "dip" into
> 10% nitric acid plus 2% hydrofluoric acid bath will enhance the development
> of this "passive" oxide."
>
>
> Tom
> www.kegkits.com
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of
> David Beierl
> Sent: Wednesday, April 21, 2010 12:53 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Hose clamps..
>
> At 10:28 AM 4/21/2010, Don Hanson wrote:
> >Besides having SS for all the parts, the marine clamps are a usually a
> >magnitude better built..but more costly, of course.
>
> Two things to watch out for in SS clamps: first, is the screw also SS?
> Second, is the clamp housing folded/crimped onto the band, or spot welded?
> Spot welding destroys the rust resistance in that area and the clamp can
> and
> does abruptly fail at the weld with no previous warning since the weld is
> invisible when the clamp is installed.  Both issues are less likely in
> clamps from a chandlery vs a FLAPS.
>
> Yours,
> David
>