Table 1-The properties and uses of common preservatives.
Standardized use |
Preservative |
Solvent Characteristics |
Surface/handling restrictions |
Color |
Odor |
Fastener corrosion |
All uses |
Creosote |
Oil-type |
Oily, not for frequent human contact |
Dark brown |
Strong, lasting |
No worse than untreated |
Ammoniacal copper zinc arsenate |
Water |
Dry, but contains arsenic |
Brown, possible blue areas |
Mild, short term |
Worse than untreated wood |
Chromated copper arsenate |
Water |
Dry, but uses are restricted by the EPA* |
Greenish brown, weathers to gray |
None |
Similar to untreated wood |
All uses (except in seawater) |
Pentachlorophenol in heavy oil |
No. 2 fuel oil |
Oily, not for frequent human contact |
Dark brown |
Strong, lasting |
No worse than untreated wood |
Copper naphthenate |
No. 2 fuel oil |
Oily, not for frequent human contact |
Green, weathers to brownish gray |
Strong, lasting |
No worse than untreated wood |
Alkaline copper quat |
Water |
Dry, okay for human contact |
Greenish brown, weathers to gray |
Mild, short term |
Worse than untreated wood |
Copper azole |
Water |
Dry, okay for human contact |
Greenish brown, weathers to gray |
Mild, short term |
Worse than untreated wood |
Aboveground, fully exposed |
Pentachlorophenol in light oil |
Mineral spirits |
Dry, okay for human contact if coated |
Light brown, weathers to gray |
Mild, short term |
No worse than untreated wood |
Oxine copper |
Mineral spirits |
Dry, okay for human contact |
Greenish brown, weathers to gray |
Mild, short term |
No worse than untreated wood |
Aboveground, partially protected (such as millwork) |
IPBC + permethrin |
Mineral spirits |
Dry, okay for human contact |
Colorless |
Mild, short term |
No worse than untreated wood |
Indoors (usually for insect protection) |
Borates |
Water |
Dry, okay for human contact |
Colorless, blue dye often added |
None |
No worse than treated wood |
*A
few uses of chromated copper arsenate are still allowed for treatment
of sawn products less than 5 inches thick (12.7 centimeters, such
as dimension lumber). Pilings, poles, large timbers, and plywood
are still allowed for highway construction.—Courtesy of USDA
Forest Service, Forest Products Laboratory |