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  • From: "Lawrence F. London, Jr." <lflondon@mindspring.com>
  • To: permaculture
  • Subject: Re: PVC/galvanized
  • Date: Wed, 12 Dec 2001 14:09:48 -0500


On Wed, 12 Dec 2001 15:30:01 +0800, Bob Howard
<rmhoward@omninet.net.au> wrote:


>Michael Dean wrote:

>> Can somebody explain to me why --"Never use lead head nails as fasteners
>> on such a roof; alternatives: stainless steel screws, also galvanized
>> screws and nails with neoprene washers"

>Corrosion is the short answer - Lead and zinc have different electrical
>potential and when water acts as a conductor between them an electric
>potential is set up and one will corrode
>the other.

Galvanized roofing and leadhead nails have been used together for over
half a century without corrosion problems and roofs that leak. As far
as I know there is no electrochemical reaction between the two that
would adversely affect a tin roof.

>This is a general problem with most metals. It is generally unwise for
>different metals to be in contact especially where there is a risk of water
>being involved. (Tho' I'm
>not sure about why stainless steel is OK on galvanized roofs %-)

These screws are separated from the roofing with a neoprene washer
which seals the nail hole and the SS won't rust anyway and (I assume)
should not react with the electroplating on the steel roofing.


L.F.London ICQ#27930345 lflondon@mindspring.com
http://www.ibiblio.org/ecolandtech london@ibiblio.org



  • Re: PVC/galvanized, Lawrence F. London, Jr., 12/10/2001
    • <Possible follow-up(s)>
    • Re: PVC/galvanized, Lawrence F. London, Jr., 12/11/2001
    • Re: PVC/galvanized, Lawrence F. London, Jr., 12/12/2001

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