What happens when copper flashing and/or nails come in contact with ACQ treated lumber in an exterior application? Is this a problem as with ferrous materials. Thanks.
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ACQ is copper based. No problem using it with copper flashing.
It is ACQ and AL or steel products that have a problem.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
While we're far better off having eliminated CCA-treated wood, it was actually much easier on fasteners than ACQ.
The chrome and arsenic in the CCA were actually corrosion inhibitors and the chromate was a water repellant. The greater amount of copper in ACQ causes galvanic corrosion and the quat is a surfactant which absorbs moisture.
Galvanic Scale (higher number will corrode lower)
1. aluminum
2. zinc
3. steel
4. iron
5. tin
6. lead
7. copper
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Thanks to all. Question. I see that zinc is actually more corrosive than steel and iron. Yet I thought that galvanizing was actually a zinc coating. How is it that galvanized nails, bolts etc. are recommended for use with ACQ. What am I missing
You mean zinc is more corrodible than steel. The zinc is like the sacrificial anode in a water heater. It attracts the corrosion to protect the other metallic parts.
http://www.galvanizeit.org/showContent,26,58.cfm#1
1. How does galvanizing protect steel from corrosion?Zinc metal used in the galvanizing process provides an impervious barrier between the steel substrate and corrosive elements in the atmosphere. It does not allow moisture and corrosive chlorides and sulfides to attack the steel. Zinc is more importantly anodic to steel - meaning it will corrode before the steel, until the zinc is entirely consumed.
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