General Corrosion Risks

Metal connectors, anchors, and fasteners will corrode and lose load carrying capacity if installed in corrosive environments or exposed to corrosive materials. Ocean salt air, fire-retardants, pressure-treated wood, fertilizers, fumes, dissimilar metals, and other elements are potentially corrosive materials that may adversely affect the load carrying capacity of these products. Connectors, anchors, and fasteners should not be installed in potentially corrosive conditions unless the product coating or metal is suitable for the intended use. Some Simpson products are available in stainless steel or with coating options that are more corrosion resistant. The most appropriate products should be carefully selected for the intended use. To further increase product durability and safety, Simpson recommends that compatible metals always be used together, including fasteners, and that the products receive frequent post-installation inspection, especially for outdoor applications. There are many variables affecting corrosion: environmental variables, including heat, moisture, humidity, rain, salt, cleaning products, proximity to bodies of water, pools, animal facilities or other corrosive environments; fire retardants, fertilizers, fumes, chemicals, and other corrosive materials and factors; wood-based variables, including wood species, moisture content, type of wood preservative, chemical carriers and additives, chemical quantities and retention levels, curing, storage, and installation.

Pressure Treated Wood

The pressure-treated wood industry has transitioned away from the use of Chromated Copper Arsenate (CCA-C) to alternative preservative systems for residential use, effective 12/31/03. Some of the replacement alternatives are generally more corrosive than CCA-C. The corrosive content of treated wood may be variable. Over time, the durability and load-carrying capacity of Simpson products used with treated woods can vary widely depending on the many variables. This makes it impossible to predict accurately if, or when, significant corrosion of connectors, anchors, and fasteners will begin or reach a critical level. The treated wood industry specifies or recommends stainless steel and hot-dip galvanized products for use with pressure treated wood. To select the appropriate connector for use with various pressure treated woods, see the Pressure Treated Wood Technical Bulletin (PDF).

Warning

While galvanized steel provides some protection, testing has shown that it is still likely to corrode if in contact with treated wood. The service life of galvanized parts depends on many variables including the location, installation, exposure, and the thickness of the galvanized coating.

Additional information

For additional critical information please see the Pressure-Treated Wood Technical Bulletin (PDF) and Pressure-Treated Wood Frequently Asked Questions.

When anticipating the use of steel connectors and fasteners with treated wood, users also should consult the treated wood chemical supplier and the wood treater for specific recommendations.