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Tricks for Treated Lumber

It's been seven years since the Environmental Protection Agency announced the phase-out of chromated-copper-arsenate (CCA)treated lumber. CCA's replacements, although safer, bring different challenges to your outdoor projects. Here's what you need to know.

Nailing deck
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4 screws
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Hot-dip galvanized fasteners have a
thicker zinc coating and therefore
provide more rust resistance than
fasteners galvanized by other
2 screws
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Stainless-steel fasteners are nearly
impervious to corrosion, but can cost
twice as much as hot-dip galvanized.
6 screws
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Some manufacturers use proprietary
anti-corrosion layers. They are often
color-matched to blend with the
wood. Many offer a lifetime guarantee
against corrosion.


CA, ACQ, MCQ, Who?

Alkaline copper quaternary (ACQ) and copper azole (CA) accepted CCA's abdication of the outdoor-lumber throne with a fairly smooth transfer of power. Both treatments provide similar, high levels of preservative power with arsenic-free chemicals.

In order to achieve the preservative power of CCA, ACQ and CA ramp up the amount of copper used. But because copper speeds corrosion in ferrous metals, steel fasteners must be chosen with care. (See photos.)

The newest kid on the block, micronized copper quat (often marked MCQ) substitutes dissolved copper with a finely ground copper particulate. While it doesn't yet have the long, proven track record of ACQ and CA, proponents claim MCQ achieves the same level of wood preservation and rot-resistance with a lowered level of fastener corrosion.

Continued on page 2:  A Chemical Bath Starts the Process


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