On Sat, 11 Sep 2010 16:10:37 -0700 (PDT),
wrote:

Normal cable clips have normal steel pins, and I've never known them
fail due to rust.

I might take a photo of the run of clips along the outside here later
on, the nail heads are just a large red rusty lump. OK they are still
holding but it's only a matter of time before they do fail and
removal will no doubt cause spalling at each one due to the
expansion.

Anything "ordinary steel" outside here will be seriously rusty within
5 years. The quality of galvanised stuff is very variable, some
things are just as installed (but not many) others are rusty.

I'm of the "if a jobs worth doing, it's worth doing properly, once".

--
Cheers
Dave.