You should have taken the physics course too. :>) The old "bumble bee
shouldn't be able to fly" is an old wives tale that has been around for
ages.
73
Gary K4FMX
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> Patrick Greenlee
> Sent: Wednesday, December 17, 2014 8:00 PM
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] A couple of 18HT questions
>
> Yeah, I had the requisite year of freshman chemistry too but lets get
> real. Hy-Gain has been making these antennas for how long? They have
> been putting aluminum into concrete for how long? Anyone ever here of a
> failure due to corrosion of the aluminum? I don't have a dog in this
> fight as I replaced the thick walled aluminum tubes with solid steel
> bars as in mounting on the roof of my barn I wanted to weld the three
> "posts" to some of my custom base components (steel) and I'm not good at
> welding steel to aluminum. I still have the aluminum tubes awaiting a
> use to present itself.
>
> Somehow I am reminded of the old story of the bumble bee and the
> aerodynamicists. :-) ;-) :-D
>
> Patrick NJ5G
>
>
> On 12/17/2014 3:36 PM, L L bahr wrote:
> > I have had my 18HT up for 30 years with aluminum tubes in the
> concrete. I see no signs of deterioration. That's good enough for me.
> >
> > Lee, w0vt
> >
> >
> >
> >
> >
> > > You do not want concrete in contact with aluminum! It will eat up
> the
> >> aluminum. Even aluminum windows come with a warning to not let the
> brick
> >> mortar come in contact with the aluminum frame when installing.
> >> After the concrete is set and dried it may be ok then, not sure.
> >>
> >> 73
> > Yes indeed.. Aluminum is readily attacked by most acids and bases: the
> > surface oxide helps a lot, and, of course, a chemical conversion
> coating
> > (anodize, alodine) would too. BUT, a scratch in the coating provides a
> > nice surface to be attacked.
> >
> > ALuminum is attacked by most basic hydroxides (e.g. sodium hydroxide,
> > lye, is used to etch aluminum panels).. It is a way to make hydrogen
> > gas, in fact.
> >
> > Mortar is a mixture of quicklime (CaO) and sand, for the most part,
> and
> > when you add water to it (slaking the lime) it forms Calcium Hydroxide
> > (Ca (OH)2).
> >
> > Concrete has similar chemistry.
> >
> > So, yes.. keep your aluminum out of the concrete footing.
> >
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