Micronized Copper Wood Preservative
You may have seen advertisements recently for a new kind of preservative-treated wood. Brand names include Yellawood MCQ, MicroPro and SmartSense. While the names are new and the properties of the wood are a little different, the preservatives used in these products are simply modified versions of existing formulations.
‘Treated wood” refers to the green-colored lumber that is widely available at hardware stores and building centers. In Tennessee , this wood is usually southern pine that has been impregnated at a factory with a copper-based wood preservative. The green color is from the copper. In the past, the copper was combined with chromium and arsenic. This “CCA” formulation was the standard for many years. About four years ago, CCA was withdrawn from residential use and replaced with alkaline copper quaternary (ACQ) and copper azole (CA). These preservatives are also copper-based but include organic co-biocides instead of chromium and arsenic. All of these formulations leave the wood green in color (unless a dye is added), clean to the touch, paintable, and protected from insect attack and rot. ACQ and CA are very corrosive to metal, however, so it is important to use only ceramic coated, stainless steel, or other approved screws and nails with treated wood.
The ‘new' products are variations on the copper/organic formulations. Instead of using dissolved copper in the preservative, small particles of copper (called ‘micronized copper') are injected into the wood. Wood treated with micronized copper is less corrosive to metal fasteners and is lighter in color. It is still important to use approved fasteners with micronized-copper treated wood but aluminum can be used in contact with the treated wood. The lighter color can be an advantage too: The wood can have a more natural look, and lighter-colored paints and stains can be used.