Handling highly corrosive flue gases like humid SO2, SO3, HCl and HF in fossil fuel power plants and waste incineration plants requires corrosion protection of carbon steel parts, especially where temperatures are at or below the dew point. These conditions are particularly challenging in the flue gas duct where heat exchangers are implemented. Linings with PFA or PVDF sheets are a proven solution for long term protection, especially at elevated temperatures. Typically the PFA sheets used for this application are 1.5 mm and 2.3 mm thick.