On 1/22/2011 1:08 PM RicodJour spake thus:

On Jan 22, 3:38 pm, wrote:

On Sat, 22 Jan 2011, RicodJour wrote:

On Jan 22, 1:59 am, David Nebenzahl
wrote:

Now *that* makes my BS meter twitch just a mite: why would
there be corrosion? Galvanized pipe is zinc over steel, so
galvanized + steel (black) should be no problem, right?

Time to recalibrate that meter, kimosabe. Zinc is used as a
sacrificial anode in boats for the very reason that it will
corrode first and protect the iron.
http://www.mikeholt.com/mojonewsarch...alvanic-Action...

YOur BS meter needs recalibrating. The ZINC may corrode, but that
is not an issue here. It is a very thin coating on one surface that
is beinf threaded to another (identical) surface. NOT an issue.
Period.

Why would the zinc corroding not be an issue?
If you have a galvanized pipe and the coating is compromised in any
way, the corrosion will be concentrated at that point, right?

This still makes no sense to me. (And just for the record, whenever I've
plumbed for gas I've used black pipe, not galvanized.)

I mean, with black pipe, the entire goddamned pipe and every fitting is
subject to corrosion, right? Except for the mill scale, or whatever
constitutes the "black" on black pipe, it's completely unprotected.
That's why we use galvanized for water. So if you use a galvanized
fitting on a run of black pipe, it sure as hell is not going to corrode
any faster than the rest of the pipe, so why sweat it *on that basis*?

There may be other reasons not to use galvanized with gas lines: all the
pros I've talked to about this lately tell me it makes no difference.
Nonetheless, most people still use black for gas.


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Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.