In Contact with Treated Wood
Pressure treated wood is often used for construction areas that will be exposed to the weather or in high moisture areas. The chemicals used to treat this wood were revised in 2003 to remove some of the potential harmful elements in the treatment. The change in chemical formulations increased the corrosivity of the wood when in contact with metal parts. The two most popular chemicals for wood pressure treatment are alkaline copper quaternary (ACQ) and copper azole (CA), which are both active corrosion materials.
Only two corrosion protection systems are recommended for use with these pressure treatment chemicals: hot-dip galvanized steel and stainless steel. The hot-dip galvanized coating provides a thicker layer of zinc than other zinc-coated fasteners. Hot-dip galvanized steel can withstand the harsh chemicals and slow the corrosion rate. Common metal parts used with pressure treated wood are connector plates, joist hangars, bracing plates, and fasteners of all types. All of these parts should be either hot-dip galvanized or fabricated using stainless steel to withstand the corrosivity of the treated wood.