Deaeration and Deactivation

In accord with principles described in Sections 7.1 and 7.2, corrosion of iron is negligible at ordinary temperatures in water that is free of dissolved oxygen. An effective practical means, consequently, for reducing corrosion of iron or steel in contact with fresh water or seawater is to reduce the dissolved oxygen content. In this way, corrosion of copper, brass, zinc, and lead is also minimized. 

Corrosion and Corrosion Control, by R. Winston Revie and Herbert H. Uhlig Copyright 2008 John Wiley Sons, Inc. 

Sodium sulfite scavenges oxygen in accord with the reaction 

Hydrazine (N2H4), supplied as a concentrated aqueous solution, also reacts with dissolved oxygen, according to 

The normal reaction products—nitrogen, water, and a small amount of NFls—are all volatile, and, unlike sulfite addition, no dissolved solids accumulate in the treated water. 

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