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Fundamentals of Corrosion
4.8.5.2 Reconstituted Wood Products
Reconstituted wood products are produced by the formation of small pieces
of wood into large sheets. The finished product can be classified as fiberboard
or particle board, depending on the nature of the basic wood component.
Fiberboards are produced from mechanical pulps. Hardwood is a relatively heavy type of fiberboard that is designed for exterior exposure.
Some reconstituted wood products can be factory primed with paint and
some may have a factory-applied topcoat to protect the wood from fungi and
insects; treatment with toxic chemicals provides the necessary protection.
A variety of materials can be used but oil and oil-borne preservatives predominate. The most widely used is coal tar creosote, which is a by-product
distilled from the coal tar produced by the high-temperature carbonization
of bituminous coal. It is a heterogeneous mixture of liquid and solid hydrocarbons. To increase penetration and reduce the coat, coal tar solutions and
creosote-petroleum solutions are used extensively. Solutions as high as 50%
have been used. A disadvantage to this type of treatment is the inability to
apply paint.
When cleanliness and paintability are required, pentachlorophenol in volatile petrochemical carriers is used. Concentrations of not less than 5% are
used. These solutions are in the same price range as coal tar emulsions and
provide the same degree of protection.
Water-borne solutions of inorganic salts are also used. These have the
advantages over the oils of greater ease of penetration and freedom from fire
hazards and odor. The disadvantage is that they cause swelling and some
react with metal. The primary preservative used is chromated zinc chloride.
Other typical salts used include:
1. Acid cupric chromate
2. Ammonial copper arsenate
3. Chromated copper arsenate
4. Chromated zinc arsenate
5. Copperized chromated zinc chloride
Wood can be treated with preservatives in several ways, including:
1. Under pressure in closed vessels
2. Dipping
3. Hot and cold soak
4. Diffusion
Of the four methods listed, treatment under pressure in closed vessels is the
predominant method employed for lumber used in engineering structures.
Fundamentals of Corrosion
4.8.5.2 Reconstituted Wood Products
Reconstituted wood products are produced by the formation of small pieces
of wood into large sheets. The finished product can be classified as fiberboard
or particle board, depending on the nature of the basic wood component.
Fiberboards are produced from mechanical pulps. Hardwood is a relatively heavy type of fiberboard that is designed for exterior exposure.
Some reconstituted wood products can be factory primed with paint and
some may have a factory-applied topcoat to protect the wood from fungi and
insects; treatment with toxic chemicals provides the necessary protection.
A variety of materials can be used but oil and oil-borne preservatives predominate. The most widely used is coal tar creosote, which is a by-product
distilled from the coal tar produced by the high-temperature carbonization
of bituminous coal. It is a heterogeneous mixture of liquid and solid hydrocarbons. To increase penetration and reduce the coat, coal tar solutions and
creosote-petroleum solutions are used extensively. Solutions as high as 50%
have been used. A disadvantage to this type of treatment is the inability to
apply paint.
When cleanliness and paintability are required, pentachlorophenol in volatile petrochemical carriers is used. Concentrations of not less than 5% are
used. These solutions are in the same price range as coal tar emulsions and
provide the same degree of protection.
Water-borne solutions of inorganic salts are also used. These have the
advantages over the oils of greater ease of penetration and freedom from fire
hazards and odor. The disadvantage is that they cause swelling and some
react with metal. The primary preservative used is chromated zinc chloride.
Other typical salts used include:
1. Acid cupric chromate
2. Ammonial copper arsenate
3. Chromated copper arsenate
4. Chromated zinc arsenate
5. Copperized chromated zinc chloride
Wood can be treated with preservatives in several ways, including:
1. Under pressure in closed vessels
2. Dipping
3. Hot and cold soak
4. Diffusion
Of the four methods listed, treatment under pressure in closed vessels is the
predominant method employed for lumber used in engineering structures.