Analysis of the causes of failure in 5Cr-1Mo pipes mounted in a preheating furnace
The oxidation resistance of iron-based alloys depends on the formation of thin protective films consisting ofreaction products between the alloys and the ambient atmosphere. The high corrosion resistance of Fe-Cr-Mo alloys hasbeen attributed to the rapid formation of a uniform, highly protective passive film. The pipes hardness and resistance tovarious forms of corrosion are determined by the composition of the oxide layer that plays an important role indetermining the lifetime of the pipes themselves. The thermal stability of the oxide layer is influenced by its compositionand thickness as well as by the bond to the underlying metal.Determining factors for the high temperature corrosion are generally: temperature, metallurgy, TAN (chloridric andnaphthenic acid), local flow conditions, sulphur compounds.