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Observation: Holes, Pits, Gouges

	Appearance	Observation	Locations	Mechanism
	General pitting	Holes, Pits, Gouges » Waterside (Firetube boiler)	Waterside of firetube boiler	Acid Attack
	ID pitting with corrosion tubercles	Holes, Pits, Gouges » Waterside	ReheaterSuperheaterWaterwall	Oxygen Pitting
	sharply defined hole	Holes, Pits, Gouges » Waterside	Economizer	Corrosion Fatigue
	Severe corrosion on side of tube facing gas turbine/duct burners	Holes, Pits, Gouges » Waterside	Evaporator Section	Multiple Under-Deposit Corrosion Mechanisms Including Caustic Gouging, Phosphate Attack, and Hydrogen Damage
	Undercut corrosion, multi-color deposits (red, white, black). (This is a view of a tube ID following cleaning.)	Holes, Pits, Gouges » Waterside	Waterwall	Acid Phosphate Attack
	Thinning on inside of a U-bend or other change in direction	Holes, Pits, Gouges » Waterside	Economizer	Flow Accelerated Corrosion (FAC)
	Defect at weld bar attachment	Fireside/Material Flaw » Holes, Pits, Gouges	Waterwall	Weld/Materials Defect
	Porosity in weld	Holes, Pits, Gouges » Material Defect	Superheater	Weld Defect
	Thinning from the fireside, pockmarks on external surface	Fireside » Holes, Pits, Gouges	Waterwall	Fireside Corrosion
	Metal wastage	Fireside » Holes, Pits, Gouges	Waterwall	Fireside Corrosion
	Thick-lipped rupture, may be very large window missing or a flap hanging by one edge	Holes, Pits, Gouges	Waterwall	Hydrogen Damage
	Deformation and perforation from the outside in	Fire/Gas Side » Holes, Pits, Gouges	Reheater	Mechanical damage
	Severe corrosion gouging at a weld-backing ring	Holes, Pits, Gouges » Water/Steam Side	Waterwall	Caustic Gouging
	Severe pock-marked corrosion on fireside	Holes, Pits, Gouges	Furnace Riser	Corrosion/Thermal Fatigue
	Appearance	Observation	Location	Mechanism