Certain metal products (including fasteners, hardware and flashing) may corrode when in direct contact with products treated with ACQ preservatives. To prevent premature corrosion and failure it is important to follow the metal products manufacturer’s recommendations.
It is important to consult the end tag to determine which preservative or preservative system was used in the treatment of that particular product in order to assure the proper fasteners are used.
Fastener Information for ACQ (Alkaline Copper Quaternary) Treated Products
ACQ Fastener Information Sheet PDF (Includes hardware manufacturers)
Fasteners (and other metal products) for use with YellaWood® brand
products with ACQ preservatives include:
- Hot-Dip Galvanized* (The minimum standard)
Fastener, hardware, and metal product manufacturers have suggested the minimum Hot-Dip Galvanized requirements for use with treated wood should conform to the following ASTM Standards: ASTM-A153 (for Hot-Dip fastener products) and ASTM-A653 (Coating Designation G-185 for Hot-Dip connector and sheet products).
- Stainless Steel
Stainless steel fasteners and connectors are required for Permanent Wood Foundations below grade and are recommended for use with treated wood in other severe exterior applications such as swimming pools, salt water exposure, etc. - Type 304 and 316 are the recommended grades to use.
- Other fasteners, hardware or any metal product as recommended by their manufacturer
There may be additional products (other than stainless steel or G-185 Hot-Dip Galvanized) which are suitable for use with ACQ treated wood. Please consult with the individual fastener, hardware, or metal product manufacturer for recommendations for use of their products with ACQ treated wood.
- Aluminum should not be used in direct contact with wood products treated with ACQ preservatives
Spacer materials or other physical barriers are recommended to prevent direct contact of ACQ treated wood with aluminum products.
Other alternative wood preservative manufacturers’ recommendations include**:
CSI fastener recommendations for use with ACQ products include:
- Hot-Dip Galvanized
- Stainless steel
- Other fasteners and hardware as recommended by the hardware manufacturer
As a minimum requirement for use with treated wood, Hot-Dip Galvanized coated fasteners should conform to ASTM Standard A153 and Hot-Dip Galvanized coated connectors should conform to ASTM Standard A653 (Class G-185). For optimum performance and longevity in treated wood, fasteners and connectors fabricated from stainless steel should be considered. Other types of screws and connectors coated with proprietary anti-corrosion technologies are also available for use with treated wood. Consult individual fastener manufacturer’s recommendations for information about the performance of their products with treated wood.
ARCH fastener recommendations for use with Copper Azole products include:
Hot-Dip Galvanized fasteners (meeting ASTM-A153) and connectors (ASTM-A653 Class G-185 sheet), or better, are recommended for protection against the moisture often present where treated wood is usually used. For Permanent Wood Foundations, use 304 or 316 stainless steel. Aluminum should not be used in direct contact with this wood.
* Electroplated galvanized fastener and metal products are typically not accepted by the building codes for use in exterior applications, regardless of the type of wood used.
** This information is correct at the time of printing.
Fastener Information for MCQ (Micronized Copper Quaternary) Treated Products
MCQ Fastener Information Sheet PDF
Micronized Copper Quaternary treated products offer many benefits including significantly improved corrosion performance. YellaWood® brand pressure treated pine with MCQ preservatives exhibits corrosion rates on metal products similar to CCA pressure treated wood and untreated wood.
- For interior or exterior applications use fasteners and hardware that are in compliance with the manufacturer’s recommendations and the building codes for their intended use.
- For exterior applications galvanized protected connectors coated at a G90 level or
its equivalent (0.90 oz./ft2) and other hardware and fasteners which meet building codes for exterior use can be used in direct contact with wood treated with MCQ preservatives.
- Aluminum building products may be placed in direct contact with YellaWood® brand products with MCQ preservatives used for interior uses and above ground exterior applications such as decks, fencing, and landscaping projects. Examples of aluminum products include siding, roofing, gutters, door and window trim, flashing, nails, fasteners and other hardware connectors. However, direct contact of MCQ treated products and aluminum building products should be limited to code-compliant construction applications that provide proper water drainage and do not allow the wood to be exposed to standing water or water immersion.
We recommend you contact the aluminum building products manufacturer for its recommendations regarding use of their aluminum products in contact with MCQ treated wood in ground contact applications or when exposed to salt water, brackish water, or chlorinated water, such as swimming pools or hot tubs.
Also check with the aluminum building products manufacturer regarding compatibility with other chemicals and cleaning agents. Contact Osmose for further information on aluminum contact use in commercial, industrial, and specialty applications such as boat construction.
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