Corrosion of fastener and connector in contact with alkaline copper treated wood – it is a problem

IRG/WP 08-40437

J N R Ruddick

For many decades, chromated copper arsenate (CCA) was the most common wood preservative used in North America for residential and industrial applications. Since December 31, 2003, the use of CCA for residential application was voluntarily terminated. One of the most widely accepted alternative wood preservatives in Western Canada is Alkaline Copper Quaternary Compound (ACQ). This paper will compare the corrosion data of CCA-treated wood with that of ACQ treated wood at a similar preservative retention. It also discusses the appropriate methodology for carrying out the corrosion studies. A modified draft American Wood Protection Association (AWPA) corrosion test method was used, where fasteners were sandwiched between two pieces of treated wood and exposed to the continuous water mist at an elevated temperature. All fasteners were tested for resistance of the coating to mechanical damage, prior to exposure. The study demonstrated that ACQ treated wood is indeed more corrosive than CCA treated wood. The study also showed that the application of water repellant to ACQ treated wood significantly reduced the corrosion rate. The best estimation of the corrosion rate was the measurement of the loss in the average core diameter in combination with a visual evaluation of the fastener and corrosion products.


Keywords: corrosion, fastener, alkaline copper, ACQ

Conference: 08-11-30/12-02 Flamingo Beach, Costa Rica


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