Flow-Accelerated Corrosion in Fossil and Combined Cycle/HRSG Plants

摘要

Flow-accelerated corrosion (FAC) has been researched for over 40 years at many locations around the world, and scientifically all the major influences are well recognized. However, the application of this science and understanding to fossil and combined cycle/HRSG plants has not been entirely satisfactory. Major failures are still occurring and the locations involved are basically the same as they were in the 1980s and 1990s. This paper reviews the mechanism of FAC with particular emphasis on fossil and combined cycle/HRSG plants. It includes discussion on a) typical locations of FAC, b) the single- and two-phase variants by describing their typical appearances in plant, c) oxides which grow in the areas of interest, d) the cycle chemistry alternatives and particularly the effect of potential (ORP) on the oxide forms, and e) the major influences on FAC of turbulence, geometry, mass transfer, and materials. Different approaches are needed within fossil and HRSG plants and these are delineated. The important differences between all-ferrous and mixed-metallurgy feedwater systems are emphasized. Overall, organizations should consolidate their inspection, predictive, and chemistry approaches into a company-wide, coordinated, multi-disciplinary FAC program.