Boiler Corrosion

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Boiler corrosion: causes and prevention

TECHNICAL BLOG

Boiler Corrosion: Causes, Risks, and Effective Prevention Methods

Corrosion causes metal loss and failures in the boiler shell, economizer, feedwater lines, and condensate return systems. Major triggers include low pH, dissolved O2 and CO2, scale/deposits, high temperature, and mechanical stress. With proper water chemistry and operational control, risks can be significantly reduced.

Causes & Typical Forms
  • Oxygen corrosion: Surface rust and pitting, especially during shutdown/startup and in feedwater lines.
  • CO2-induced acidic condensate: General thinning and grooving in condensate lines.
  • Alkalinity/pH deviations: Low pH accelerates general corrosion; uncontrolled high pH can damage aluminum or brass surfaces.
  • Under-deposit corrosion: Localized corrosion cells and hot spot damage under scale/sludge deposits.
  • Galvanic/stress effects: Localized attacks accelerated by dissimilar metals or thermal stresses.
Effective Preventive Measures (Field Applications)
  • Degasser + oxygen scavenger: Reduce O2/CO2 with a thermal degasser, then polish with scavengers such as sulfite or sodium bisulfite.
  • pH/Alkalinity control: Manage phosphate and alkalinity levels within the FO/KO range; use neutralizing amines on the condensate side.
  • Filming amine/protective coating: Apply an organic protective film transported by condensate to reduce metal surface wetting.
  • Blowdown optimization: Use TDS/conductivity sensors for automatic surface blowdown; remove sludge through bottom blowdown to minimize heat loss.
  • Deposit management: Employ pre-treatment (softening/RO), phosphate programs, regular sludge removal, and heat transfer surface cleaning.
  • Operation & maintenance: Apply wet/dry preservation during shutdowns, ensure proper startup procedures, promptly repair leaks, and maintain consistent analysis logs.
O₂ / CO₂
Main triggers
pH & TDS
Continuous monitoring
Blowdown
Automatic / optimized
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