Re: [TowerTalk] A couple of 18HT questions

[Patrick Greenlee <patrick_g@windstream.net>]

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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