Abstract
A survey of the literature was performed for the Electric Power Research Institute on Corrosion Related Failures in Flue Gas Desulfurization (FGD) Systems. It was found that pitting and crevice corrosion of alloys occurred throughout scrubbers and were the major cause of failure. Stress-corrosion cracking failures were found in the prescrubber and in the reheater while erosion-corrosion failures occurred most frequently in the prescrubber. Pitting and crevice corrosion were associated with the presence of chlorides and low pH conditions while these factors, in conjunction with higher temperatures, appeared to be responsible for the occurrence of stress-corrosion cracking. Erosion-corrosion failures were associated with high velocities and the presence of particulates in the incoming flue gas.
Failures of organic linings occurred primarily as a result of debonding, caused by temperature upsets, and, occasionally, as a result of improper application. Erosion-corrosion failures of organic linings also were reported. Failures of inorganic linings have occurred as a result of improper materials selection and permeability to aqueous solutions.
Solutions to these problems generally are dependent upon the specific application. The nickel-base alloys that contain molybdenum are highly resistant to pitting, crevice corrosion, erosion-corrosion and stresscorrosion cracking, but are expensive and difficult to fabricate. Recently- developed organic coatings, such as the fluoroelastomers, are much more tolerant of temperature upsets than are the organic coatings that are commonly used, but the former are difficult to successfully apply. Acid resistant bricks and mortars are much more resistant to attack in scrubbers than are calcium aluminate concrete and mortars or portland cement. However, protection of the underlying carbon steel support structure continues to be a problem with inorganic linings.
