Creosote

Definition - What does Creosote mean?

This is a corrosive, gummy and enormously combustible substance that forms when the volatile gases, which are products of burning wood (beech wood or creosote bush) or coal tar combine and condense below 250° F. It has the following properties:

  • A foul smell
  • Combustible
  • Gum properties
  • It can exist as solid or liquid depending on the temperatures
  • Corrosive in nature

This material is present in chimneys and pipes that guide exhaust gases out of a furnace or oven. It is used as wood preservative in utility posts and railroad ties.

Corrosionpedia explains Creosote

The buildup of creosote is very common on the walls of metal fireplace chimney systems when incomplete combustion occurs for a certain period of time. Cool flue temperature is a key cause of the formation of creosote as flue gases come into contact with the surfaces of the flue. Creosote occurs in three forms, which include:

  • Soot – fine black dust
  • Crunchy and porous creosote
  • Tar-like creosote – sticky and drippy with a shiny glaze

One preventative measure against the formation of Creosote is by maintaining a temperature of above 250 °F to prevent the gases from condensing. The buildup of Creosote may affect the velocity of flow in the guides and hence increase the chemical reaction and acid formation. The gases can be burnt up before they reach the chimney or pipe, hence reducing the formation of this substance.

By reducing the water content in the wood, the burning will contain less moisture content that cools the chimney that leads to the condensation of the volatile gases. Creosote corrodes metals like steel and iron when they combine with moisture to form acids. Therefore, separation of metals from creosote-treated wood materials prevents corrosion.

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