A Practical Guide to Material Compatibility for Marine Urea (AUS40)

Protecting Your SCR System Integrity

As the maritime industry deepens its commitment to decarbonization, Marine Urea (AUS40) has become indispensable for compliance with NOx emission regulations. This high-purity solution is the lifeblood of Selective Catalytic Reduction (SCR) systems, but its effectiveness—and the longevity of the entire system—hinges on a critical factor: material compatibility. Using incompatible materials for storage tanks, pipes, and seals can lead to contamination of the urea, corrosion of equipment, and ultimately, costly failure of the SCR system.

This guide provides clear, practical advice on selecting the right materials for handling AUS40, ensuring operational reliability and safeguarding your environmental compliance.

Why Material Compatibility is Non-Negotiable

AUS40 is a 40% urea solution in demineralized water. While not classified as hazardous, it can be corrosive to certain metals and plastics over time. The primary risks of material incompatibility are:

• Contamination of Urea: Leaching of ions (like copper, zinc, or aluminum) from incompatible metals can poison the catalyst in the SCR system, rendering it ineffective.
• Equipment Failure: Corrosion and material degradation can cause leaks in tanks, pipes, and seals, leading to operational downtime and safety hazards.
• Loss of Compliance: A compromised SCR system will fail to reduce NOx emissions to the levels mandated by IMO Tier III and other regulations, putting the vessel at risk of non-compliance.

The international standard ISO 18611 provides detailed guidelines on the materials required for handling and storing urea solutions, serving as the definitive reference for the industry.

Recommended Materials for AUS40 Service

Based on extensive testing and industry standards, the following materials have proven to be highly compatible and are recommended for direct contact with Marine Urea.

Materials to Strictly Avoid

Using incompatible materials is a common cause of SCR system failure. The following materials must NEVER come into direct contact with Marine Urea:

• Carbon Steel
• Copper and Copper Alloys (Brass, Bronze)
• Zinc (Galvanized Steel)
• Aluminum
• Certain Plastics and Rubbers (e.g., PVC)

Conclusion: A Foundation for Reliability

Effective NOx reduction is a pillar of modern sustainable shipping. While Marine Urea is the agent of this change, its performance is only as reliable as the system that contains it. By diligently adhering to material compatibility guidelines outlined in ISO 18611 and following industry best practices, shipowners and operators can ensure the long-term reliability of their SCR systems, maintain environmental compliance, and sail confidently towards a cleaner maritime future.