Control of dissolved oxygen in the boiler feedwater is of paramount importance to effectively prevent corrosion of carbon steel and copper alloy materials in industrial steam water cycles. The principals of thermomechanical and chemical deaeration of steam generator feedwaters in low (< 300 psig), medium (301 to 600 psig) and high (> 901 psig) pressure system will be covered. Tray type and spray type deaerators and other degasification equipment performance expectations will be discussed. The capabilities of numerous generically available oxygen scavenger/reducing agent products widely used in industrial systems are presented as well as providing methods for general corrosion, localized corrosion, flow assisted corrosion control and for metal surface passivation. Plant best practices for operational control to avoid feedwater and overall steam generation system corrosion are also discussed. Trouble shooting techniques available to achieve operational best practices and control are provided.

KEY WORDS: Feedwater system, feedwater heater, economizer, degasification, deaeration,
spray-tray, spray-scrubber, vortex breaker, pressure reducing station (PRS), pressure reducing
valve (PRV), chemical feed distributor, heat recovery steam generator (HRSG), waste heat boiler
(WHB), net positive suction head (NPSH), universal gas sizing equation, approach temperature,
saturation temperature, venting rates, Charles’s Law, Dalton’s Law, Henry Constants,
metallurgy, forms of corrosion, pitting, thinning, collapse, exfolitation, erosion corrosion,
corrosion fatigue, crevice corrosion, flow accelerated corrosion (FAC), under deposit corrosion
(UDC), internal chemical treatment regimes, chemical oxygen scavengers, metal passivators,
neutralizing amine, ammonia, filming amine, continuous dissolved oxygen analysis, trouble
shooting.