In the past years, wood consumption from native forests has drastically reduced the availability of wood. Fast-growing species such as Pinus and Eucalyptus suitably impregnated with chemicals may show a service life equal or higher than hardwood with high natural durability. The field tests have been an alternative widely used to evaluate the durability of wood and the efficiency of preservatives. In the present study, visual analysis was applied to assess the resistance of fence posts and efficiency of chemical preservatives after 20 years in the field tests. The grade sound of fence posts of Eucalyptus saligna, Eucalyptus grandis, Pinus elliottii, and Sclerolobium paniculatum was evaluated. The samples were submitted to nonpressure treatments using a mixture of creosote and used motor oil by immersion in hot and cold solution and a formulation based on fluor/chrome/arsenate/phenol by a diffusion processes. Creosote and CCA-C were the chemicals applied in the pressure treatment using the Bethel process. For each wood species/chemical combination, 10 samples were treated and other 10 samples were used as a control. Among the control wooden fence posts, S. paniculatum showed the highest natural durability followed by E grandis, E. saligna and P. elliottii. Hot and cold bath treatment using a mixture of creosote and used motor oil was more efficient than diffusion process. S. paniculatum were also the most resistant fence posts among samples treated without pressure followed by E. grandis, P. elliottii and E. saligna. Creosote was the most efficient chemical among the pressure treatments and S. paniculatum the most resistant fence posts followed by E. grandis and P. elliottii.

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