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Dissolved Oxygen & Pitting Corrosion in Steam Boilers: A Water Treatment Approach
Dissolved oxygen carried in the feed water creates small but deep pits in the boiler pipes. Selection of mechanical deaeration and chemical oxygen scavenger.
Dissolved oxygen carried in steam boiler feed water is one of the main causes of pitting corrosion, which creates small-scale but deep pits, especially on hot metal surfaces. This damage is concentrated in narrow areas instead of progressing homogeneously over the entire metal surface; Therefore, even if the overall metal thickness of the boiler seems good, sudden punctures may occur in the smoke pipes, economizer or feed line.
As the temperature increases, the corrosive reaction rate of oxygen increases. Air leaks in the system, decrease in deaerator temperature, frequent cold make-up water entry and lack of wet/dry protection during standby periods are the main operating factors that increase the risk.
The first step of the correct conditioning approach is to read the deaerator (thermal deaerator) operating temperature and pressure together with the feed water analyses. Chemical oxygen scavengers are activated to bind the trace amounts of dissolved oxygen remaining after mechanical deaeration and to support the protective passive magnetite (Fe₃O₄) layer on the metal surface.
Elif Çevre Kimya's boiler chemicals page includes oxygen scavengers such as DEHA (Diethylhydroxylamine), carbohydrazide and catalyzed sodium sulfite. While volatile organic oxygen scavengers (such as DEHA) can be transported to the steam line without adding additional conductivity to the boiler water; Sulphite-based products are evaluated according to boiler pressure, blowdown regime and point of use of steam.
Suitable product; It should be determined according to boiler operating pressure, feed water temperature, condensate return rate, direct contact of steam with the process and material structure. pH, conductivity, total iron transport and oxygen scavenging balance measurements should be recorded regularly. Fixed dosage or performance cannot be guaranteed without reviewing water analysis and facility operating data.
Why Is Dissolved Oxygen a Critical Puncture Risk?
Dissolved oxygen carried in steam boiler feed water is one of the main causes of pitting corrosion, which creates small-scale but deep pits, especially on hot metal surfaces. This damage is concentrated in narrow areas instead of progressing homogeneously over the entire metal surface; Therefore, even if the overall metal thickness of the boiler seems good, sudden punctures may occur in the smoke pipes, economizer or feed line. As the temperature increases, the corrosive reaction rate of oxygen increases. Air leaks in the system, decrease in deaerator temperature, frequent cold make-up water entry and lack of wet/dry protection during standby periods are the main operating factors that increase the risk.
Mechanical Deaeration and Chemical Oxygen Scavenger Compatibility
The first step of the correct conditioning approach is to read the deaerator (thermal deaerator) operating temperature and pressure together with the feed water analyses. Chemical oxygen scavengers are activated to bind the trace amounts of dissolved oxygen remaining after mechanical deaeration and to support the protective passive magnetite (Fe₃O₄) layer on the metal surface. Elif Çevre Kimya's boiler chemicals page includes oxygen scavengers such as DEHA (Diethylhydroxylamine), carbohydrazide and catalyzed sodium sulfite. While volatile organic oxygen scavengers (such as DEHA) can be transported to the steam line without adding additional conductivity to the boiler water; Sulphite-based products are evaluated according to boiler pressure, blowdown regime and point of use of steam.
Conditioning Works Not Alone, But With Regular Monitoring
Suitable product; It should be determined according to boiler operating pressure, feed water temperature, condensate return rate, direct contact of steam with the process and material structure. pH, conductivity, total iron transport and oxygen scavenging balance measurements should be recorded regularly. Fixed dosage or performance cannot be guaranteed without reviewing water analysis and facility operating data.
Field Control and Monitoring List
Chemical dosage and system capacity decisions should be determined by analysis and facility conditions; There is no guarantee of fixed dosage or performance.
- Control of deaerator dome temperature, working pressure and vent valve
- Air leakage / cavitation control in feed water tank and pump suction lines
- Selection of volatile (DEHA) or inorganic oxygen scavengers according to boiler operating pressure and steam usage purpose
- Monitoring pH, conductivity and dissolved/total iron in feedwater and boiler blowdown water
- Definition of wet or dry protection procedure for boilers waiting at standstill
- Check out the Boiler Water Chemicals Page
- Boiler Feed Water Analysis & Request a Quote
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