Wood Preservation

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Wood Preservation
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Wood enemies

• Wood staining fungi
• Wood decay fungi types
• Brown rots
• White rots
• Soft rots

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Wood Enemies Borers - Beetles

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Wood Enemies Termites

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Characteristics of wood preservatives

• Toxicity - poisonous to fungi and insects
• Penetration capacity
• Fixation capacity chemically stable
• Retention capacity
• Distribution in the wood
• Availability
• Economical
• Eco friendly
• Should not Leached into soil and water

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Wood Preservative Chemicals

• Tar oil Preservative eg. Creosote
• Organic solvent Preservatives
• Water-borne Preservatives

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Tar oil Preservative eg. Creosote

• Railway Sleepers Transmission Poles
• USA STC
  Kaldemulla 2010
• S

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Tar oil Preservative eg. Creosote

• Produced as distillate of coal tar
• Very effective against wide range of organisms
• Pressure-treated timber service life of 30 -50
  years even in high hazard situations
• But odour, taint food not suitable for indoor
  use
• Treated wood cannot be painted, surface becomes
  greasy

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Tar oil Preservative eg. Creosote

• In Sri Lanka STC use creosote to treat railway
  sleepers and transmission poles
• Decline in creosote use in some countries

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Organic solvent preservatives

• Biocidal (Insecticides or fungicides) dissolved
  in organic solvent
• Solvent can be
• Oily type (heavy fuel oil)
• Medium heavy type (kerosene or petrol)
• Light type (white spirits)
• Applied by brushing, dipping, spraying or double
  vacuum treatment

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Organic solvent preservatives
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Organic solvent preservatives

• Used as pre-treatment of building timber
• Used as remedial treatment of wood in buildings
  following fungal or insect infestations

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Fungicides in Organic solvent preservatives

• Pentachlorophenol PCP Na PCP
• Effective fungicide
• Used to control blue stain
• attack of rubberwood
• Now banned
• Cu and Zn Naphthenates -

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Insecticides in Organic solvent preservatives

• Chlorinated hydrocarbons
• Aldrin, dieldrin - Banned in many countries
  (persistent in env)
• Lindane
• Organophospahtes
• Synthetic pyrethroids
• Permenthryn, cypermethrin,
• deltamethrin

Low persistence in env. Low mammalian toxicity.
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Insecticides in Organic solvent preservatives

• Synthetic pyrethroids
• Has contact toxicity for range of wood borers
• Used as pretreatment of construction timber

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Water Borne Preservatives

• Aqueous solutions of toxic salts
• They are odourless
• Leave the wood clean
• Wood can be paintable after treatment
• Two types
• Unfixed eg. Boron compound
• Fixed eg. CCA

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Celcure - CCA
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Water Borne PreservativesBoron compounds

• Boric acid and borax (disodium tetraborate)
  mixure
• Diffusion treatment of rubberwood with boron
  first invented in Sri Lanka
• Green timber immerse in solution for short time
  closed stacked under plastic sheets
• Not fixed. Leached.
• Not suitable to use in buildings

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Water Borne PreservativesCopper-chromium-arsenic
(CCA)

• Most effective preservative against fungi,
  insects and marine borers.
• Service life or more than 30 years in hazard
  conditions
• Use to treat railway sleepers, poles, building
  timber.

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CCA treatment_at_ Finlay Rentokil, Wattala (2009)
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Water Borne PreservativesCopper-chromium-arsenic
(CCA)

• Use of CCA banned in Sri Lanka
• STC still use CCA
• Finlay Rentokil use CCB (Copper-chrome-boron)
• Other Cu preservatives CCB, CCF, CCP

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Drying before preservationSTC, 2010
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CCA treatment vessel_at_ Finlay Rentokil, Wattala
(2009)
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CCA treatment vessel_at_ Finlay Rentokil, Wattala
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Chrome-Azurol-SBlue colour penetraion
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Creosote treated Poles
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Treatment Methods

• Brush, spraying, and dip (immersion)
• Sap-displacement method
• Vacuum Pressure Impregnation
• Hot and cold open tank
• Full cell (Bethell)
• Empty cell
• Double vacuum