Abstract

Under water vapor exposure between 551-5610C, Fe-9Cr ferritic-martensitic steel form a triplex oxide scale made of an outer magnetite layer surrounded by a hematite layer and an inner Fe-Cr rich spinel layer. Long time oxidation test campaign has revealed that buckling and spallation of the outer oxide scale always occur during isothermal oxidation or cooling down to room temperature. The interfacial zone of delamination has been proved to be located inside the magnetite layer, where a void belt is formed and grows. It is assumed that voids are the preponderant factor initiating decohesion of the magnetite layer under compressive stresses during the oxide scale growth. The location of voids accumulation has been precisely determined by calculating the distribution of cationic vacancy flux in a duplex oxide scale.

Keywords:
flowline corrosion, riser corrosion, oxide scale, materials and corrosion, oxidation, mechanism, subsurface corrosion, delaminated area, publication division, texas 77084
Subjects:
Pipelines, Flowlines and Risers, Materials and corrosion, Well Integrity, Subsurface corrosion (tubing, casing, completion equipment, conductor)
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2015. NACE International
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