Pressure-treated lumber is treated with Alkaline Copper Quaternary (ACQ), an environmentally friendly, water-based preservative that is free of arsenic and chromium.
However, ACQ treated lumber is more corrosive to metal, so the right fastener is key to a safe, long lasting deck, fence or other outdoor project.
According to Tree Island Steel — a North American manufacturer and supplier of premium steel wire and wire products for a broad range of industrial, OEM, commercial construction, residential, and agricultural applications — when nails are exposed to ACQ, a chemical reaction occurs.
This reaction accelerates the corrosion rate of the fastener. Additionally, the organic components of ACQ attract water, further increasing corrosion on the fastener.
The wood treatment industry recognizes the corrosive nature of ACQ in relation to fastening systems, and recommends hot-dipped galvanized or stainless steel nails be used. Hot-dipped galvanized nails must meet American Society for Testing and Materials (ASTM) A153 Class D standards and stainless steel nails should be made from grade 304 or 316 — providing maximum corrosion protection.
So, if screws are used for such application, then they must be rated for ACQ. Tree Island Steel’s ZincGard hot-dipped galvanized nails are recommended for use in exterior applications and in ACQ pressure treated lumber.
The company produces over 400 sizes, shapes, and finishes and all nails meet ASTM F1667, ASTM A153, and ASTM C514 standards.