Even with good deaerating heater operation, sufficient dissolved oxygen can remain in feedwater to damage the boiler system. Low levels of dissolved oxygen are critical to highpressure (high temperature) systems. Oxygen in water produces pitting which is particularl severe because of its localised nature. Economisers and feedwater heaters areM especially susceptible to oxygen attack. While CorTrol OS5601 can effectively be used in low-pressure boilers systems, it was developed as an oxygen scavenger for higher pressure applications where boiler water solids are a major concern.