Re: [Paddlewise] Stainless Hardware (was: Cleaning fibreglass kayaks)

From: "Steve Scherrer" <flatpick_at_teleport.com>

> Thanks Dave!  Seems like I read that the more rust resistant SS is the
> softer/ weaker the alloy.  es correcto?  hence the poor edge holding
> capabilities of this *rust proof* knife.

Stainless steel is a relatively "granular" metal.  This, coupled with
some brittleness in certain alloys, leads to an metal that tends not 
to hold an edge.  A crude analogy is the difference between flint 
and sandstone - one can take a fine sharp edge, the other cannot.

This leads to other properties as well.  Most stainless alloys
cannot be tested easily with ultrasonics.  The structure of the 
metal scatters the sound internally.

One thing that frustrates me about most stainless knives is that
it's almost impossible to sharpen the knife to what it was like
when new.

I have a Japanese kitchen knife that is stainless wrapped around
a soft steel core.  The cutting edge exposes the core and it is 
what gets sharpened.  This knife is the sharpest in the kitchen
and is great to use.  The core is easy to distinguish visually, as
it has a dark color due to a small amount of corrosion that is
not worth removing.  This is not a knife that you can leave to 
air dry or it will rust quickly.

BTW, Dave's comments on crevice corrosion helps explain why sailboats
have corrosion problems on multistrand shrouds and stays.  The 
stainless cable has lots of crevice and the fittings at the end
of the cable add even more little cubbyholes for corrosion to occur.

Mike
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