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 |
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