Re: [Paddlewise] The stainless thread

Randy Ricchi <rricchi_at_houghton.k12.mi.us> wrote:

>>I know from my homebrewing experience that household bleach is VERY
corrosive to stainless steel. Now, the active ingredient in household
bleach is sodium hypochlorite, which may be somewhat different from the
chlorine they use in swimming pools, but I've always wondered if those who
practice rolling during the winter months in swimming pools should be
concerned about any stainless parts on their kayaks.
Perhaps those on this list with more knowledge of these matters could
comment?>>

The concentration of chlorine in pool water is very low, somewhat higher
than that in tap water, so the damage to your SS fittings is likely to be
small, especially if you rinse well.  Even so, you should pull some of the
deck hardware and check now and then.  In addition, if your kayak has SS
cables for rudder control, I'd replace them every second year or so.

(Note:  I do not follow my own advice:  I have copper-sleeved SS cables in
my Wind Dancer that have been in service since 1997; they are a second set.
The first set lasted from 1993 to 1997.  A buddy replaced his SS cables when
they cratered (not at the sleeves, but inside the yak, some 5-6 inches from
the rear entry) in 1998 after 12 years of service.  Replacing cables every
two-three years is very safe, IMHO, but I do carry a spare.)

Others have emphasized the need to minimize the contact of dissimilar
metals, but as Steve Scherrer points out, copper sleeves on SS cable and
wire have been a marine industry standard for years, and hold up well in
service.  The green sheen that builds up at the sleeve/cable contact is
evidence for slight corrosion of  _the copper_, and not the SS, which
(perversely) might be __protected__ from crevice corrosion by this practice.
This may seem counter to the normal advice of placing a "more active"
sacrificial metal in contact with the metal you want to preserve.  But,
remember that to remain protected, the SS has to maintain an __oxide__
coating on its surface (actually on the chromium and other alloying metals),
so it has to remain as anode.  Adjacent copper, which is less active than
iron, may ensure this.

I honestly do not know what happens inside a copper sleeve over SS cable,
and have never seen any cross-sections of that arrangement after several
years of service.  Anybody got a picture of what one looks like?

I'm guessing the "usual" guess re: dissimilar metals may not be the best
practice for sleeves on SS cable, though I do agree aluminum is a really
terrible choice for sleeving unless massive (which I think I may have seen
on some large diameter wire rope on draggers around here).

This sleeve business is a mystery to me, but most agree metallurgy is one of
the technical disciplines where good theory sucks, and practical experience
rules.

--
Dave Kruger
Astoria, OR

***************************************************************************
PaddleWise Paddling Mailing List - Any opinions or suggestions expressed
here are solely those of the writer(s). You must assume the entire
responsibility for reliance upon them. All postings copyright the author.
Submissions:     PaddleWise_at_PaddleWise.net
Subscriptions:   PaddleWise-request_at_PaddleWise.net
Website:         http://www.paddlewise.net/
***************************************************************************