Efficacy of a borax-copper preservative in exposed applications

Abstract

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Efficacy of alternative copper-based preservatives in protecting decking from biodegradation

“…The sodium silicate addition to BC appeared to lessen the extent of surface discoloration to some extent but this was difficult to evaluate in later stages of the study because of decay development. Comparison of decay development in decking in this study to that of Mississippi in-ground stake specimens from an earlier report (Lebow et al 2009) shows the great difference in decay hazard between the types of exposure and exposure locations (Table 5). For example, decay was not detected in any decking specimens treated with 2,34 % BC until year 18, while this condition was reached within the first year in the Mississippi stake exposure.…”

“…Permanence of the boron and copper in the treated wood is a consideration and it is expected that the type of outdoor exposure (above-ground versus ground-contact) will affect both efficacy and permanence. Stake tests installed in Mississippi and Wisconsin indicated that BC does not provide adequate protection at the concentrations evaluated (Lebow et al 2009). Failures were particularly rapid at the Mississippi test site and appeared to be associated with boron depletion and subsequent colonization by copper-tolerant fungi.…”

“…Failures were particularly rapid at the Mississippi test site and appeared to be associated with boron depletion and subsequent colonization by copper-tolerant fungi. It should be noted that the stakes used in that study were 19 mm by 19 mm by 457 mm, and that these small dimensions likely contributed to rapid boron depletion (Lebow et al 2009).…”

“…This research has been conducted and indicates that BC is adaptable to pressure treatment (Lebow et al 2005a) and is effective in protecting wood against decay and termites in laboratory and covered ground proximity tests Lebow et al 2005b, Lebow et al 2006, Woodward et al 2002. However, laboratory leaching tests also indicated that 45 % -55 % of the boron and 5 % -6 % of copper was depleted from specimens during exposure to 750 mm of simulated rainfall (Lebow et al 2009). This suggests that boron could be largely depleted from wood exposed to precipitation after a few years in areas with moderate rainfall or even more rapidly in wet climates.…”

“…Although neither of these formulations provided adequate protection for wood placed in contact with the ground (Lebow et al 2009, above-ground exposure typically represents a much less severe biodeterioration hazard (Kirker and Winandy 2014). In addition, ground-contact failures in both formulations appeared to be at least partially associated with copper-tolerant fungi, and there is some evidence that there is less risk of degradation by copper-tolerant fungi in treated wood used above ground (Choi et al 2002).…”