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permaculture - Re: PVC/galvanized

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Chronological Thread  
  • From: Bob Howard <rmhoward@omninet.net.au>
  • To: permaculture <permaculture@franklin.oit.unc.edu>
  • Subject: Re: PVC/galvanized
  • Date: Wed, 12 Dec 2001 15:30:01 +0800




Michael Dean wrote:

> Howzit,
>
> 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"
>
> Cheers Mike.
>

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. 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 %-)

Bob










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