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Preservative-Treated Wood and Alternative Products in the Forest Service

Corrosiveness of Treatments

Because the pressure-treated wood industry has been phasing out CCA and using alternative chemicals for treatment, the potential corrosiveness (figure 10) of alternative wood preservatives needs to be considered. Hot-dipped galvanized fasteners meeting the ASTM A153 standard and connectors meeting the ASTM A653 Class G185 sheet-steel standard are recommended for protection against the effects of moisture when treated wood is used.

Aluminum should not be used in direct contact with wood treated with copper-based preservatives. One fastener manufacturer, Simpson Strong-Tie, has conducted its own tests. Simpson found that some of the alternative treatments were slightly more corrosive than CCA. A report can be found on Simpson's Web site: http://www.strongtie.com/productuse/corrosion.html.

The Forest Service Forest Products Laboratory is studying the corrosiveness of alternative wood preservatives and may provide some guidance.

Photo of a corroding metal plate on a bridge constructed with preservative-treated wood.
Figure 10—This metal plate used in a stress-laminated bridge
constructed with preservative- treated wood shows the early
signs of corrosion.—Photo courtesy of James Wacker