Dissolved Gases

In Boiler Water

How dissolved gases are dangerous for your boiler?

In addition to other contaminants, natural water or raw water that is directly sourced from resources has various gases dissolved in it. These gases are produced by atmospheric air. In terms of boiler feed water, we are primarily concerned with oxygen and carbon dioxide, but other gases still make up a modest portion. These gases have an effect on the lifespan and operation of the boiler. Oxygen causes corrosion, which eventually causes the system to fail. It also lowers the quality of the steam, uses more fuel, reduces efficiency, and causes steam leakage. which is undesirable for a boiler operation that runs smoothly.


Oxygen Pitting

Below is a detailed description of how oxygen and carbon dioxide affect boiler performance.

Effect of oxygen

One of the most dangerous gases in water is oxygen; even a relatively small amount can seriously destroy the boiler system. It causes rust and corrosion known as oxygen pitting or oxygen attack when it reacts with iron-carbon steel. Oxygen is more corrosive at higher temperatures. This oxygen attack may be localized or contained to a specific area, which ultimately results in system failure or leakage.

Pits are small, localized corrosion spaces created by oxygen. Oxygen pits may quickly "drill" through metal surfaces, which causes metal to become worn down and fail. The iron surface dissolves as oxygen corrodes the boiler metal. In addition to weakening the metal site, this also introduces dissolved iron into the boiler. This dispersed iron can build up on boiler tubes, scorching them and leading to tube failure.


Temperature and pressure affect how soluble oxygen is in water; at constant pressure, solubility reduces as temperature rises, whereas at constant temperature, solubility rises with pressure.

Effect of Temperature on Corrosion

When temperatures are high, oxygen becomes more corrosive and breaks down metal more quickly than when temperatures are low. This accelerates the system's breakdown.

Effect of carbon dioxide:

Because the deaeration process removes the gases from the feed water, the make-up water after deaeration often has no CO2 content. It is the condensate that contains CO2 most frequently, therefore the condensate tank quite often experiences CO2 corrosion. The decomposition of carbonate and bicarbonate in condensate under boiler conditions is typically what causes the presence of the gas in condensate. Both oxygen and free carbon dioxide can be removed from the feed water by heating it in the feed tank and keeping it there while it is being delivered to the boiler.