Ken, You have brought up a great subject. While I doubt zinc coated spokes will provide significant galvanic protection for frames, I have seen the tragic effects of inadequate consideration of the corrosion promotion caused by dissimilar metals.
If things are kept in dry environments, it is possible to connect stainless steel components to steel components and get away with it. Add in typical humidity, or worse, rain, and time, presto, corrosion.
The solutions are: consideration of the galvanic potential of the components and fasteners used, electrical isolation, diligent use of coatings (temporary fix at best - given adequate galvanic potential and plenty of moisture the best coatings can be quickly driven off), use of sacrificial anodes (alluded to by Ken, but not really practical), or desiccation. My vote is to consider the galvanic potential of the materials when selecting components and fasteners. In appreciating the excellence of engineering of these classics, one thing I admire is the correct use of alloys.
Jon M. Crate FAI Materials Testing Laboratory Marietta, Georgia 30066
-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of Ken Sent: Wednesday, September 02, 2009 12:43 PM To: classicrendezvous@bikelist.org Subject: Re: [CR] Galvanised spokes
Hi John,
I had not thought of galvanised spokes providing "sacrificial galvanic" protection to a steel bike frame but if there is a good electrical connection between the wheels and frame then that is indeed what would happen with the spoke galvanising corroding in preference to the frame.
The reason that I mention this is that most galvanised spokes are eventually replaced with stainless spokes which does not afford the same level of galvanic protection and so does that mean that frames that have stood the test of time might now corrode away in front of our eyes.
Should we be fitting small strips of zinc to our cherished bikes ?
Regards
Ken Hume London, England
> John Hurley wrote:
>
> I've often wondered how certain
> steel items are protected if they aren't stainless, chromed or
> galvanized. Saddle rails and spokes come to mind. Zinc is effective,
> of course, but can be pretty dingy-looking. Maybe some of you amateur
> (or professional) metallurgist-types can comment.
>
> John Hurley
> Austin, Texas, USA