The problem is the integrity and continuity of the coating. I think that it
is sold for its color, with no guarantee about pin holes, continuity. Pins
holes will result in bimetallic reaction, and since the new coatings are
further from copper on the activity chart, any damage will be faster - and
I seen many cases of pitting of lcc resulting in more rapid deterioration
than straight copper.
Dr. Judith E. Selwyn
Preservation Technology Associates, Inc.
285 Reservoir Road
Chestnut Hill, MA 02467
617 598-2255
fax 617 277-3389
[log in to unmask]
----- Original Message -----
From: "Hammarberg, Eric" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, July 11, 2007 8:53 AM
Subject: Re: [BP] Terne coated COPPER Roofing
> Leland
>
> Thanks, we have a galvanic chart but this one is nice and simple.
>
> The material we are considering is not zinc but coated copper. I have not
> given much thought to using zinc for roofing as copper and stainless have
> such a good local track record. Do you like zinc?
>
>
> Thanks,
>
> Eric Hammarberg
> Vice President
> Thornton Tomasetti
> 51 Madison Avenue
> New York, NY 10010
> T 917.661.7800 F 917.661.7801
> D 917.661.8160
> [log in to unmask]
>
> This message sent from Treo, please pardon spelling and other mistakes.
>
> -----Original Message-----
> From: Leland Torrence [mailto:[log in to unmask]]
> Sent: Tuesday, July 10, 2007 06:01 AM Eastern Standard Time
> To: [log in to unmask]
> Subject: Re: [BP] Terne coated COPPER Roofing
>
> Eric,
>
> Attached below is a good simple chart for galvanic reactions. As for
> Zinc,
> maybe you already know, but the detailing is very different from copper.
> You can't have any old tin knocker do Zinc. You also have to watch for
> design details and what would promote ripping, cracking/splitting or white
> rust. I prefer Rheinzink. They also have a pretty good book
> "Applications
> in Architecture".
>
> Best,
>
> Leland
>
>
>
> Design Handbook: Section 1
> Fundamentals: Architectural Considerations
> ----------------------------------------------------------------------------
> ----
>
> Weathering, Corrosion, Staining, Substrate, Solder, Sealants
>
> One of the most important issues concerning the use of copper is the
> chemical reaction between copper and other materials. Chemical reactions
> are
> responsible for corrosion, staining, and even the green patina that
> develops
> on copper surfaces over time.
>
> Weathering and Patination:
> The oxidation process that gives copper its characteristic green patina is
> a
> result of exposure to an acidic atmosphere. The process is, therefore,
> faster in some metropolitan, marine, and industrial areas, where higher
> concentrations of pollutants exist. When acidic moisture comes in contact
> with exposed copper surfaces, it reacts with the copper to form copper
> sulfate. The acid is neutralized during the reaction with the copper. This
> patina eventually covers the surface and adheres tightly to it, thus
> providing a protective layer against further weathering.
>
>
> Corrosion:
> All metals have a property called nobility. It is a measure of a metal's
> resistance to corrosion when in contact with another metal. A greater
> relative difference in nobility between the two metals in contact
> indicates
> a greater corrosion potential. Table 1.1.4 ranks the most common metals
> used
> in construction in increasing nobility, called the galvanic number.
>
> Table 1.1.4 - The Nobility of Common Metals
>
>
> 1. Aluminum
> 2. Zinc
> 3. Steel
> 4. Iron
> 5. Stainless Steel - Active
> 6. Tin
> 7. Lead
> 8. Copper
> 9. Stainless Steel - Passive
>
> When dissimilar metals are in contact with one another in the presence of
> an
> electrolyte, galvanic action occurs, resulting in the deterioration of the
> metal with the lower galvanic number. The electrolyte may be rain water
> running from one surface to another, or moisture from the air containing
> enough acid to cause it to act as an electrolyte.
>
>
>
>
>
> Leland R. S. Torrence
>
> Leland Torrence Enterprises and the Guild
>
> 17 Vernon Court, Woodbridge, CT 06525
>
> Office: 203-397-8505
>
> Fax: 203-389-7516
>
> Pager: 860-340-2174
>
> Mobile: 203-981-4004
>
> E-mail: [log in to unmask]
>
> www.LelandTorrenceEnterprises.com
>
>
>
> _____
>
> From: This conversation may be monitored for quality control.
> [mailto:[log in to unmask]] On Behalf Of Jim Hicks
> Sent: Monday, July 09, 2007 5:54 PM
> To: [log in to unmask]
> Subject: Re: [BP] Terne coated COPPER Roofing
>
>
>
> On 7/9/07 9:12 AM, "Hammarberg, Eric" <[log in to unmask]>
> wrote:
>
> Yes folks it appears that this is Freedom Gray by Revere - Tin/Zinc
> Coated.
> Is there any reason to be concerned about galvanic action?
>
>
> Eric Hammarberg, Assoc. AIA
> Vice President
> Thornton Tomasetti
> 51 Madison Avenue
> New York, NY 10010
> T 917.661.7800 F 917.661.7801
> D 917.661.8160
> [log in to unmask]
>
>
>
> _____________________________________________
> From: Hammarberg, Eric
> Sent: Friday, July 06, 2007 2:06 PM
> To: 'The Listserv that makes holes in Manhattan schist for free!'
> Subject: Terne coated COPPER Roofing
>
> Does anybody have an opinion of Terne coated COPPER Roofing?
>
> Thanks,
>
>
> Eric Hammarberg, Assoc. AIA
> Vice President
> Thornton Tomasetti
> 51 Madison Avenue
> New York, NY 10010
> T 917.661.7800 F 917.661.7801
> D 917.661.8160
> [log in to unmask]
>
>
>
> <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
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>
> I think for galvanic action you need surfaces next to each other to have
> an
> oxidation process occur with each surface that effecting the other. When
> two
> metals are fused like tin/zinc on copper there isn't a surface to be
> interacted on.
> j
>
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