In　coal-fired　boilers,　low-temperature　corrosion　occurring　in　the　back-end　is　always　threatening.　Particularly,　the　desulfurized　flue　gas　from　outlet　of　the　flue　gas　desulfurization　(FGD)　unit　is　quite　aggressive.　The　flue　gas　reheater　placed　after　FGD　is　usually　operating　under　a　much　more　severe　condition　than　the　condensing　heat　exchangers　before　FGD.　In　this　paper,　field　corrosion　tests　were　conducted　in　a　coal-fired　heating　plant　and　tubular　corrosion　probes　made　of　different　grades　of　steels　were　tested.　The　total　testing　period　was　6　weeks.　The　corroded　probes　were　then　analyzed　by　X-ray　fluorescence　(XRF),　X-ray　diffraction　(XRD),　scanning　electron　microscope　(SEM)　and　energy　dispersive　spectrometer　(EDS),　and　the　deposition　and　corrosion　mechanisms　were　studied.　The　droplets　entrained　by　the　flue　gas　resulted　in　deposition　and　corrosion　on　the　probe,　especially　on　the　windward　side.　During　the　tests,　2507　and　2205　showed　good　corrosion　resistance,　while　ND,　304L,　316L　suffered　considerable　corrosion.