On 22/01/2020 22:42, Jim Wilkins wrote:
"Richard Smith" wrote in message
...
"Jim Wilkins" writes:

....
Thanks. I've acquired a heap of galvanized tubing that might become
an
upgrade to my 50' antenna mast, and was wondering if I'd missed a
reason why welding on a structure was discouraged, since it's how
ships are built.
* you'd burn the galv away around the weld - and the weld never has
any galv (spray with zinc-based paint - which will need
periodically
reapiring / re-applying)

* you are not supposed to weld over galv. Zink toxicity & disturbs
arc (arc goes a lilac colour) & could affect weld strength and
fusion
We went over this a while ago, and I asked you what you paint on the
weld because the brush-on zinc-rich paint I have lets rust bleed
through after a year or three, even though I sandblasted the area
clean first. I then sprayed on waxy LPS-3 which kept the rust from
expanding, but it seems to need some existing rust to soak into or it
washes off.

The goop that does last outdoors is Ox-Gard, for aluminium electrical
connections. The element and feed connections on my antennas remain at
a few milliOhms for many years after scrubbing them and quickly
applying it. I measure the resistance with a voltmeter while 1.00A
flows through the joint, 1mV = 1 milliOhm. I had to drill out the
rivets and install aluminium screws and nuts.

Our digital TV reception is much better than the old analog, and TVs
aren't taxed in the USA, however almost everyone prefers to pay
$150/month and up for cable. Antenna reception is pretty much a
do-it-yourself project with no repairmen to call. This British digital
receiver with the spectrum analyzer program is a great aid in aiming
the antenna to minimize multipath.
https://www.sdrplay.com/rsp1a/


I used some Rustoleum aerosol cold zinc spray on some outdoor galvanised
steel I had to weld and after cleaning and applying 5 years on no sign
of any rust.