⚡ Oxygen Corrosion in Pumps
Corrosion is one of the most common problems affecting pumps and piping systems. Among the different types of corrosion, oxygen corrosion is particularly aggressive, especially when oxygen is present in hot water. Even small concentrations of dissolved oxygen can cause serious damage to pump components, reducing efficiency and shortening equipment life.
🌡️ Why Oxygen Causes Corrosion
- Oxygen is a highly reactive element. When dissolved in water, it participates in electrochemical reactions on the metal surface.
- In the basic mechanism of iron corrosion:
- Oxygen from the air dissolves in water.
- At the cathode, oxygen ions receive electrons instead of hydrogen ions.
- This reaction leads to the formation of iron oxides (rust).
- The resulting potential is considerably higher than that of hydrogen corrosion, meaning oxygen can attack metals that are normally resistant to acid corrosion.
🔍 Characteristics of Oxygen Corrosion
- Accelerated Corrosion Rate: Oxygen increases the rate of metal deterioration compared to other forms of corrosion.
- Rust Formation: Iron surfaces exposed to oxygen-rich water develop rust layers that weaken structural integrity.
- Attack on Resistant Metals: Even metals not typically affected by acid corrosion can be attacked when oxygen is present.
📊 Oxygen Levels and Corrosion Rate
- Normal oxygen concentration in freshwater: 6–8 ppm.
- At this level, the corrosion rate of iron in freshwater is approximately 0.2–0.5 mm per year, depending on operating conditions.
- Temperature Effect: Higher water temperatures accelerate chemical reactions, increasing corrosion.
- Velocity Effect: High fluid velocity increases the amount of oxygen reaching the metal surface, further raising the corrosion rate.
⚙️ Impact on Pumps
- Reduced Efficiency: Corroded surfaces increase friction losses and reduce hydraulic efficiency.
- Component Damage: Pump casings, impellers, and shafts are vulnerable to oxygen attack.
- Maintenance Costs: Frequent repairs and replacements are required if oxygen corrosion is not controlled.
- System Reliability: Severe corrosion can lead to leaks, breakdowns, and unplanned downtime.
🛠️ Preventive Measures
- Deaeration: Remove dissolved oxygen from water before it enters the pump system.
- Chemical Treatment: Use oxygen scavengers (like sodium sulfite) to neutralize dissolved oxygen.
- Protective Coatings: Apply anti-corrosion coatings or linings to pump surfaces.
- Material Selection: Use corrosion-resistant alloys or stainless steel where oxygen exposure is unavoidable.
- Regular Maintenance: Inspect and clean pumps to prevent dirt and deposits that accelerate corrosion.
✅ Conclusion
Oxygen corrosion is a serious issue in pump systems, especially when handling hot water or high-velocity flows. Even small amounts of dissolved oxygen can significantly increase corrosion rates, leading to rust formation, reduced efficiency, and costly maintenance. By understanding the mechanisms of oxygen corrosion and applying preventive measures such as deaeration, chemical treatment, and proper material selection, industries can extend pump life and ensure reliable operation.
