Using Aluminum Monarch Z Clips with ACQ Treated Wood

When you use Monarch Z Clips with ACQ treated wood, you need to be careful.

ACQ is an acronym for Alkaline Copper Quaternary, and ACQ treated wood is wood treated with a preservative that protects against rot, fungal decay and termite attack. ACQ treated wood products are commonly used for projects such as decks and fencing. ACQ products have a dark, greenish color to begin with and will age to trun light tan/brown color with exposure to sunlight, eventually fading to a grayish color. The copper and quaternary compounds are applied to the wood by pressure and are effective fungicides and termiticides.

The trick comes in using this type of wood with aluminum. The copper in the ACQ treated wood interacts with the dis-similar aluminum through a galvanic interaction. The standard Monarch Z Clips are made from aluminum. Galvanic corrosion occurs when dissimilar metals come into contact with one another in the presence of moisture. An electrochemical reaction occurs between the copper and the aluminum and one material loses electrons and corrodes as the anode, while the other one gains electrons as the cathode.

Alternatives for using Monarch Z Clips with ACQ treated wood include using our Stainless Steel Monarch Z Clips (available in 304 alloy standard and 316 Marine Grade Stainless Steel by special order) or to use a hot dip galvanized steel. Another alternative would be to use a polyethylene barrier with a minimum thickness of 10 mils. Whichever clip you select, you should also take care in selecting the appropriate screw to use with the clip.