In order to minimize boiler system corrosion, an understanding of the operational requirements for all critical system components is necessary.īoiler feedwater heaters are designed to improve boiler efficiency by extracting heat from streams such as boiler water blowdown and turbine extraction or excess exhaust steam. The consensus is that feedwater oxygen, iron, and copper content should be very low (e.g., less than 7 ppb oxygen, 20 ppb iron, and 15 ppb copper for a 900 psig boiler) and that pH should be maintained between 8.5 and 9.5 for system corrosion protection. The ASME Consensus for Industrial Boilers (see Chapter 13) specifies maximum levels of contaminants for corrosion and deposition control in boiler systems. Proper treatment of boiler feedwater effectively protects against corrosion of feedwater heaters, economizers, and deaerators. Some have stainless steel superheater elements. Many have copper alloy and/or stainless steel feedwater heaters and condensers. Most industrial boiler and feedwater systems are constructed of carbon steel. proper precautions during start-up and shutdownĬORROSION TENDENCIES OF BOILER SYSTEM COMPONENTS.operation within design specifications, especially for temperature and pressure.control of oxygen and boiler feedwater contamination.maintenance of proper pH and alkalinity levels.These conditions may be controlled through the following procedures: The most common causes of corrosion are dissolved gases (primarily oxygen and carbon dioxide), under-deposit attack, low pH, and attack of areas weakened by mechanical stress, leading to stress and fatigue cracking. Methods of corrosion control vary depending upon the type of corrosion encountered.

Other common problem areas include deaerators, feedwater heaters, and economizers. Many corrosion problems occur in the hottest areas of the boiler-the water wall, screen, and superheater tubes. It is estimated that problems due to boiler system corrosion cost industry billions of dollars per year.

Corrosion Protection during Downtime and StorageĬorrosion is one of the main causes of reduced reliability in steam generating systems.

Mechanical Conditions Affecting Corrosion.

Corrosion Tendencies of Boiler System Components.

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