Why Flue Lining Corrodes  

Normally solid fuels have to have a greater flue surface area inside the chimney than others as they produce a larger quantity of toxic gases and combust at higher temperatures.   

The flue lining inside the chimney is subjected to very high temperatures that eventually affect the joints of the flue as well as the surface of it. This results in leakage and can be dangerous as carbon monoxide can escape. Therefore, it is vital to ensure that your flue liner is checked regularly.

The decline in integrity is conditional on the material used in flue structure. If you don't regularly sweep the flue in your chimney a build up of tar can reduce the effectiveness of the flue and even cause chimney fires.

Liquid fuels burn off at less hot temperatures in the flue; however they do leave an appreciable quantity of damp and often acid residuals in the chimney. It seems that, since the productions of burning cool off earlier than solid fuel gasses in the flue a dew point is arrived at leading to acid condensations dripping backwards down within the flue liner. This stimulates erosion of the flue liner, jointing.

There are, naturally, many alternate causes for a leaky flue liner other than those related to the working process of boilers and fires for any period of time. For example, badly installed flues can cause leakages that can cause real worries over health.

Always ensure that you have hired a competent workman to carry out any work on your flue and chimney. Blockages that will cause flue gas instability are very common and you should visually check that the chimney cap is in place. If these are missing it can mean that birds nests etc can block the flow and result in the burning process being hindered.