Stanley 14"x10' Pocket Tape Rule By Tools 33115

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Fact Sheet American Wood Council

Engineered and Traditional Wood Products

Fastener Corrosion Background Starting January 1, 2004, Chromated Copper Arsenate (CCA) treated wood products were no longer permitted to be manufactured for general sale, with only some minor exceptions for use in limited, well-defined applications. (See http://www.epa.gov/pesticides/factsheets/chemicals/cca_transition.htm for more information.). Some of the commonly available preservative-treated wood products will be treated with ammoniacal copper quat (ACQ), copper azole (CBA/CA-B), or ammoniacal copper zinc arsenate (ACZA). While these alternative treating chemicals have been proven to be effective wood preservatives when used in accordance with AWPA standards, there is some evidence that these chemicals are more corrosive than CCA to metal fasteners and connectors. The purpose of this document is to provide answers to some specific questions related to this issue. Users are cautioned that this information is only a synthesis of reports currently available from public sources. A number of sources are attempting to assess the corrosivity of treatment chemicals. Updates will be issued as new or additional information becomes available.

Questions & Answers Q: Lumber treated with CCA has been available for many years. Does metal corrode in contact with CCA treated lumber? A: The chemicals used in CCA treated lumber have been shown to be somewhat corrosive to fasteners and connectors. Accordingly, chemical manufacturers and the treated lumber industry have traditionally recommended and the model building codes have required the use of corrosion resistant fasteners and connectors when used with CCA treated lumber. Q: What’s different with the new alternative treatments? A: When subjected to standardized laboratory tests that accelerate the corrosion process, metal connectors and fasteners exposed to the chemicals used in ACQ, Copper Azole, or ACZA exhibit higher rates of corrosion than connectors and fasteners exposed to CCA. Discussions within the affected industries are attempting to sort out the significance of these differences in real-world applications. Q: What should users do while the technical issues are being evaluated? A: At the very least, users should rigorously apply the recommendations of the chemical manufacturers and the treating industry – to use corrosion resistant fasteners and connectors or zinc-coated (galvanized) fasteners and connectors with corrosion protection at least equivalent to that of hot-dip galvanized products.

Copyright © 2005 American Forest & Paper Association, Inc.

August 2005

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Q: What zinc coating specifications apply to hot-dip galvanized products used in wood building construction? A: Specifications for sheet metal connectors (joist hangers and metal straps) and fasteners (such as nails and bolts) are addressed in separate ASTM standards. Coating weight designations for sheet steel are specified in ASTM A 653, Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process. An example zinc coating designation in ASTM A 653 is G185 where “G” indicates zinc coating and “185” indicates a total of 1.85 oz/ft2 of coating on both sides of the steel sheet. For fasteners, minimum coating weights are specified in ASTM A 153, Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware. A Class D designation applies for fasteners 3/8” in diameter and smaller. The minimum coating weight associated with Class D is 1.0 oz/ft2. Q: Is there a difference between “hot-dip” galvanized products and other types of galvanized products manufactured using a different process? A: There are a variety of processes for galvanizing metal products other than the hot-dip process. These include electrolysis (electrogalvanized, zinc plated) and peening (mechanical plating). There are some differences and issues that users should be aware of: 1) Coating thicknesses developed by the electrolysis process may be too thin. Most commonly available elect