Corrosion is one of the main causes of reduced
reliability in steam generating systems. It is estimated
that problems due to boiler system corrosion cost
industry billions of pounds per year.
Many corrosion problems occur in the hottest areas of
the boiler-the water wall, screen, and superheater
tubes. Other common problem areas include de-aerators,
feedwater heaters, and economisers.
Methods of corrosion control vary depending upon the
type of corrosion encountered. 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.
These conditions may be controlled through the
following procedures:
- maintenance of proper pH and alkalinity levels.
- control of oxygen and boiler feedwater
contamination.
- reduction of mechanical stresses.
- operation within design specifications,
especially for temperature and pressure.
- proper precautions during start-up and shutdown.
- effective monitoring and control.
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