[TowerTalk] Iron <-> copper tinned : Redox reaction??

Sat Nov 25 01:51:02 EST 2006

..."No it is not...
It is really raw iron as I wrote the same use for rebar (the iron which
goes in the concrete, is this the wrong term rebar?)".....

Ok.  That's a surprise. Yes, rebar is the correct term for the iron used 
in concrete.  I can't imagine a tower made out of the stuff. Usually you 
need something with more strength.

The only way to protect steel is to protect it from water, or coat it 
with a plating that is less noble than the steel. That's one reason zinc 
plating is used for galvanizing, which will sacrifice itself saving the 
steel when they are both exposed to water. If you do not have water the 
steel should not corrode. You can paint it, but it needs to be a really 
good paint.  If water gets thru the paint, the steel will corrode 
inside, causing more cracks in the paint and accelerating the process.

Since aluminum, steel, and copper are fairly close together on the 
series, I think you could use any of these for a clamp. Since steel 
corrodes so easily, the best bet is to seal this junction very well 
against water, and don't have air trapped inside with whatever you 
sealed it with. Add a good coating of anti-oxidant such as Noalox 
between the two metals. The anti-oxidant will help keep water out and it 
will improve contact because these anti-oxidants usually contain zinc.
------------

.."That's the problem. What I can get here where I live (Argentina) the
most is tin plated clamps ...
But I will have a look aroung maybe some special vender has other stuff 
..."...

I don't know if you need to clamp to a round surface or a flat surface. 
You may have to make a clamp. Just pick the best metals. If you find an 
aluminum clamp that will work that is tin plated and you need aluminum 
you can always grind off the plating.

-----------------

The data in the table below came from the galvanic series for metals 
which you can find on the internet. There was one error in the previous 
table I posted for copper, so I will repeat the table.

In the galvanic series, in flowing sea water, in order from least noble
to more noble:
Zinc is -.98 to -1.03
Aluminum alloys are -.76 to -1.0
Steel is -0.60 to -0.71
Copper is -.3 to -.57
Tin is -.3 to -.33 and
Stainless steel varies a lot depending upon the alloy and may be -.57 to 
0.0.
---------

..."I already was thinking if I put apart an lightning conductor instead to
use the tower itself.
Do you have a seperate lightning conductor for you tower?
I tought to put the lightning conductor isolated from the tower down and
use this also as ground for the equipment...
Is this a good or bad idea?".....

I don't think that will help.  The inductance of anything like this that 
you add will be much higher that than the inductance of the tower. If 
you add it, most of the current from a lightning strike will still go 
down the tower. I think this is a wasted effort. A good ground system 
tied to the tower at the base is all you need.

----------
..."Do you mean the ground wire which is in the earth or the ground wire
which comes from the tower?
And I don't right understand you did  put aluminum entrance panel but
you used copper wires for the grounding
system, right? Is this because of there are only ground roads of copper
and you want the corroding site not below
the earth? Because if not so why not use aluminum wire for the grounding
system?"......

Copper ground rods and copper wire was used, cadwelded together, then an 
aluminum clamp was used to attach the copper wire to the galvanized 
tower. It was sealed to protect it from water because the aluminum to 
copper junction is susceptible to corrosion. The zinc to aluminum 
junction is also susceptible but to a lesser degree. 

Aluminum wire is not a good choice for below ground because SOME soils 
will attack the aluminum and cause it to corrode very quickly. Copper 
will last much longer. You also don't want aluminum wire attached to 
copper rods, and I don't think there is an easy way to attach aluminum 
wire to aluminum rods even if your soil doesn't corrode aluminum.

Jerry, K4SAV

Beat Meier wrote:

>K4SAV wrote:
>
>  
>
>>I'm assuming your tower is really galvanized steel and not raw iron.
>>
>> 
>>
>>    
>>
>No it is not...
>It is really raw iron as I wrote the same use for rebar (the iron which 
>goes in the concrete, is this the wrong term rebar?)
>
>  
>
>>I posted this message about a year ago. It seems to go against 
>>conventional wisdom around here, but I got no response from anyone.  
>>Maybe the info is correct (seems correct to me), or maybe no one wanted 
>>to make the effort to reply. Anyway here it is again.
>>
>>The way most people do it is to put a stainless steel shim between the 
>>zinc tower and the copper wire and clamp it.  Polyphaser makes clamps 
>>that work like that.
>>
>>That said, doing it this way doesn't make any sense to me. You have at 
>>least three goals in avoiding galvanic corrosion.
>>1) Maximize the contact area of the least noble metal exposed to the 
>>electrolyte (water),
>>2) Minimize the potential difference between the metals in contact, and
>>3) Keep the water out.
>>
>>1) The least noble metal in this case is the zinc tower, but the contact 
>>area is the same for both metals because water may collect within the 
>>junction but the whole tower is not going to immersed in a liquid. So 
>>item 1 (in the case of what is in contact with the tower) is a moot point.
>>
>>2) The least noble metal will corrode.  The higher the potential 
>>difference, the faster it will corrode. If you look at the small list 
>>below, you will see this is the zinc (your tower). In order to avoid 
>>this you should put something as closely matched to the tower as 
>>possible, and let whatever comes next do the corroding (you can easily 
>>replace that, if need be).
>>
>>In the galvanic series, in flowing sea water, in order from least noble 
>>to more noble:
>>zinc is -.98 to -1.03
>>aluminum alloys are -.76 to -1.0
>>copper is -.3 to -.37
>>tin is -.3 to -.33 and
>>stainless steel varies a lot depending upon the alloy and may be -.57 to
>>0.0.
>> 
>>
>>    
>>
>Where did you get this values?
>An of course in my case if I have a raw iron tower - is there any 
>material which corrodes instead of the iron?
>As I understand all materials here are more noble and therefore my tower 
>will corrode :-(
>I already was thinking if I put apart an lightning conductor instead to 
>use the tower itself.
>Do you have a seperate lightning conductor for you tower?
>I tought to put the lightning conductor isolated from the tower down and 
>use this also as ground for the equipment...
>Is this a good or bad idea?
>
>  
>
>>Looking at this table, I can't figure out why people use stainless steel 
>>next the their towers. I would think an aluminum alloy would be a better 
>>choice. After going through this exercise, I decided to use one of the 
>>standard AC entrance panel aluminum alloy ground lugs (Home depot, 
>>Lowes, or any electrical house), since my tower requires a clamp that 
>>can be mated to a flat surface. I think some of these may be tin plated, 
>>others are not.  Don't use the tin plated ones. I used an oversized 
>> 
>>
>>    
>>
>That's the problem. What I can get here where I live (Argentina) the 
>most is tin plated clamps ...
>But I will have a look aroung maybe some special vender has other stuff ...
>
>  
>
>>clamp because I liked the robust clamping screw it had. I bent the end 
>>of my #4 ground wire into a tight J loop, which I placed under the screw 
>> 
>>
>>    
>>
>Do you mean the ground wire which is in the earth or the ground wire 
>which comes from the tower?
>And I don't right understand you did  put aluminum entrance panel but 
>you used copper wires for the grounding
>system, right? Is this because of there are only ground roads of copper 
>and you want the corroding site not below
>the earth? Because if not so why not use aluminum wire for the grounding 
>system?
>
>  
>
>>to gain more surface contact area. When you tighten the clamping screw, 
>>the copper wire actually squashes into the aluminum a little.  These 
>>clamps work well under a tower bolt after you file off the little ridge 
>>on the bottom of the clamp, and you will probably have to drill the 
>>mounting hole larger.
>>
>>I coated the aluminum alloy to copper junction with an anti-oxidant and 
>>sealed it against water.  I used duct seal to encapsulate the whole thing.
>>
>> 
>>
>>    
>>
>Yes that's the way I want to do. I wantg paint it with a very good 
>(expensive) anti-oxidant which is used for cars
>and over that a very good painture
>
>Thanks a lot for your help!! I really don't know which way to go that my 
>tower will work many years right.
>And here nobody has much idea about that!!!
>
>Beat
>
>  
>
>>Jerry, K4SAV
>>
>>Beat Meier wrote:
>>
>> 
>>
>>    
>>
>>>Hello
>>>
>>>I want connect my tower parts (6m each part) with a copper wire 35mm² 
>>>each leg (3 legs).
>>>How can I do that?
>>>I get copper tinned stuff with bolts which can press the copper wire on 
>>>one end and
>>>at the other end I can put it to the iron tower and paint the whole stuff.
>>>But my question is: Does the iron react with the tinned copper?
>>>And more over: If I would use cadwelding which creates copper arround 
>>>the connections
>>>this really would react havely with iron ...
>>>
>>>So what does you guys do to connect "something" to iron towers?
>>>BTW: The iron is the same as used for rebar ...
>>>Would it better to use some stuff of aluminium or stainless?
>>>
>>>Other question for the chemicals: What is the clue with the chemical 
>>>table of the elements i.e. which metals don't react with
>>>others like Gold (Au), Silver(ag),  Copper (Cu)
>>>This are all in the same column (11) but iron is in column 8  and Tin in 
>>>column (14) so what chemical values are importend to see if there
>>>is a redox reaction?
>>>
>>>Thanks for any infos
>>>
>>>Beat
>>>_______________________________________________
>>>
>>>
>>>
>>>_______________________________________________
>>>TowerTalk mailing list
>>>TowerTalk at contesting.com
>>>http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>>>
>>>
>>>   
>>>
>>>      
>>>
>>_______________________________________________
>>
>>
>>
>>_______________________________________________
>>TowerTalk mailing list
>>TowerTalk at contesting.com
>>http://lists.contesting.com/mailman/listinfo/towertalk
>>
>> 
>>
>>    
>>
>
>_______________________________________________
>
>
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk at contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>
>  
>