After concern about the toxicity of CCA-treated lumber led manufacturers to voluntarily phase it out of general use in January 2004, a new problem emerged: The less-toxic, copper-based preservatives that replaced CCA — such as ACQ and copper azole — were much more corrosive to metal fasteners and connectors. (Galvanic corrosion, as it's called, occurs when dissimilar metals like copper and steel — or copper and the zinc coating on galvanized steel — come into contact in the presence of water.) Connector maker Simpson Strong-Tie launched a campaign to make builders and consumers aware of the issue and ramped up production of corrosion-resistant stainless steel and heavily galvanized connectors.

However, the recent introduction of lumber treated with a copper-free preservative has the potential to greatly reduce such concerns. Generically known as PTI (for the chemicals propiconazole, tebuconazole, and imidacloprid), the new compound was developed by Georgia-based Arch Wood Protection, which markets the treated lumber under the trade...

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