On Sat, 22 Jan 2011 21:22:14 -0800 (PST), Harry K
wrote:

On Jan 21, 10:59Â*pm, David Nebenzahl wrote:
On 1/21/2011 9:58 PM RicodJour spake thus:

I would not mix galvanized and black iron directly, even if it's
allowed, as that accelerates corrosion. Â*You'd have to use a
dielectric fitting.

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?

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Comment on quaint Usenet customs, from Usenet:

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

To add to that. The "zinc" on the galvanised never touches the "black
iron". Threading removes the zinc plating in that area and the
fittings never screw together far enough for the zinc to touch the
unplated pipe/fitting.

Harry K
More or less true - but "some" galvanized fittings appear to have
zinc in the female threaded portion.
Not with hot dip galvanizing, for sure - but in "bright zinc"
"galvanizing".

This does not change the fact that the zinc is NOT a corrosion risk.