Forest Products Laboratory

Title: Efficacy of a borax-copper preservative in exposed applications

Author: Lebow, Stan T.; Lebow, Patricia K.; Woodward, Bessie M.; Halverson, Steven A.; Abbott, William; West, Michael M.

Date: 2009

Source: Research paper FPL-RP-655

Station ID: RP-FPL-655

Description: 

This study evaluated the ability of pressure treatments with a borax–copper (BC) preservative to protect wood exposed above ground or in contact with the ground. Stake testing indicated that the 2.3% and 4.7% BC concentrations were fairly effective in preventing decay in Wisconsin but were not effective in protecting stakes exposed in Mississippi. The 1.4% and 2.3% BC concentrations effectively protected decking specimens exposed for 5 years at the Wisconsin test site. Assay of stakes at the Wisconsin site indicated that over 90% of boron in the below-ground portion of the stakes was lost within the first year, leaving copper as the sole biocide. Assay of the decking specimens after 4 years of exposure indicated that between 30% and 45% of copper and 80% and 95% of boron was lost from the BC-treated decking specimens. These copper losses were greater than those found with the laboratory simulated rainfall study, which indicated that 5% to 6% of copper was lost from the 1.4% and 2.3% BC treatments after the equivalent of 1 year of rainfall. Boron losses of 45% to 55% were noted with 1 year’s equivalent of simulated rainfall. This series of stud­ies indicates that the efficacy of BC as a pressure-treatment preservative in exposed applications is a function of copper retention.

Keywords: Preservatives, copper borates, stake tests, leaching, borax, copper, preserved wood, evaluation, wood preservation, wooden buildings, borax-copper, pressure-treated wood, above-ground, ground-contact, durability, leaching

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Citation

Lebow, Stan T.; Lebow, Patricia K.; Woodward, Bessie M.; Halverson, Steven A.; Abbott, William; West, Michael M.  2009.  Efficacy of a borax-copper preservative in exposed applications.   Research paper FPL-RP-655.