Nickel-Copper Alloy Pipe Intergranular Corrosion Prevention for Seawater Desalination

1. Introduction: Corrosion Challenges in Desalination Equipment

Seawater desalination equipment runs in harsh corrosive environments.

High salinity, dissolved oxygen and temperature changes accelerate pipe aging.

Nickel-copper alloy pipes are core components for desalination systems.

They outperform ordinary stainless steel in seawater corrosion resistance.

However, intergranular corrosion remains a common and hidden failure issue.

This corrosion occurs along metal grain boundaries, causing internal cracking.

It leads to pipe leakage, reduced equipment efficiency and high maintenance costs.

Effective prevention measures are essential for long-term stable operation of desalination equipment.

2. Understanding Intergranular Corrosion of Nickel-Copper Alloys

2.1 Basic Characteristics

Intergranular corrosion targets grain boundaries instead of metal surfaces.

External pipe surfaces remain intact in the early corrosion stage.

Internal grain structure gradually loosens and loses mechanical strength.

Sudden pipe rupture often occurs without obvious early warning signs.

2.2 Main Trigger Factors

Unreasonable heat treatment during pipe production and welding.

Long-term exposure to high-salinity seawater medium.

Fluctuations in water temperature and dissolved oxygen content.

Improper post-weld cooling and residual internal stress.

3. Material Selection Optimization Prevention

3.1 Adopt Qualified Anti-Corrosion Alloy Grades

Select standard nickel-copper alloys with stable grain structure.

Avoid low-purity materials with uneven element distribution.

Qualified grades reduce grain boundary precipitation and corrosion sensitivity.

3.2 Strict Raw Material Inspection

Check material composition and mechanical reports before installation.

Reject unqualified pipes with grain defects and impurity aggregation.

Ensure raw materials meet desalination equipment industry standards.

4. Processing and Welding Process Control

4.1 Standardize Welding Operations

Avoid overheating and long-time high-temperature baking during welding.

Control welding temperature within the safe range of 800–1000℃.

Prevent grain boundary carbide precipitation caused by high temperature.

4.2 Optimize Heat Treatment Process

Perform solution annealing after welding and pipe forming.

Eliminate residual stress and restore uniform grain structure.

Greatly reduce the risk of intergranular corrosion activation.

4.3 Avoid Cold Working Excessively

Excessive cold bending and extrusion cause grain boundary deformation.

Controlled cold processing minimizes structural defects.

5. Operation and Maintenance Prevention Measures

5.1 Stabilize Desalination Water Quality Parameters

Control seawater salinity and chlorine ion concentration steadily.

Avoid sharp fluctuations of dissolved oxygen and water temperature.

Reduce long-term extreme corrosion stimulation on pipe grain boundaries.

5.2 Regular Cleaning and Passivation Treatment

Clean pipe inner walls regularly to remove salt scale and sediment.

Sediment accumulation easily causes local concentrated corrosion.

Regular chemical passivation forms a protective film on alloy surfaces.

5.3 Periodic Non-Destructive Testing

Use ultrasonic and metallographic detection for regular inspection.

Check internal grain status and early corrosion traces.

Realize early discovery and advanced maintenance.

6. Common Construction and Operation Mistakes to Avoid

Avoid random high-temperature welding without post-weld heat treatment.

Do not use unqualified auxiliary welding materials.

Prevent long-term shutdown and seawater stagnation inside pipes.

Avoid frequent drastic changes of equipment operating parameters.

7. Practical Application Benefits

Standardized prevention measures effectively control intergranular corrosion.

Extend the service life of nickel-copper alloy pipes significantly.

Reduce unexpected equipment shutdown and pipe replacement costs.

Improve the overall operational stability of seawater desalination systems.

8. Conclusion

Intergranular corrosion is a key hidden danger for nickel-copper alloy pipes in seawater desalination equipment.

It can be effectively prevented through standardized material selection, precise welding and heat treatment control.

Stable water quality operation and regular testing also play indispensable roles.

Full-process prevention measures avoid internal structural damage of alloy pipes.

For desalination projects, these measures ensure long-term, safe and low-cost system operation.

They provide reliable technical guarantees for the stable operation of marine water treatment equipment.

The above content was generated by AI assistance.