How to Store DEF and Marine Urea (AUS40): A Complete Guide

Proper storage of high-purity urea solutions like Diesel Exhaust Fluid (DEF/AdBlue®) and Marine Urea (AUS40) is critical. It’s not just about maintaining the fluid's quality—it's about protecting expensive Selective Catalytic Reduction (SCR) systems, ensuring regulatory compliance, and maximizing your investment.

This guide provides clear, actionable best practices for storing urea solutions to ensure their longevity and effectiveness.

The Golden Rule: Temperature Control is Everything

Temperature is the single most important factor affecting the shelf life and quality of your urea solution. Both extreme heat and cold present challenges.

1. High Temperatures (The Shelf-Life Killer)

Heat accelerates the hydrolysis process, where urea and water break down into ammonia. This reduces the fluid's effectiveness and can lead to SCR system faults.

• Ideal Range: Store urea between -5°C and 25°C (23°F and 77°F) to maximize shelf life.
• Avoid Direct Sunlight: Never store containers in direct sunlight. The UV rays and radiant heat will rapidly degrade the solution.
• Ventilation: Ensure storage areas are well-ventilated to prevent heat buildup.

2. Low Temperatures (The Freezing Point)

Urea solution will freeze, but unlike many other fluids, freezing does not permanently damage it.

• DEF (AUS32) Freezing Point: Approximately -11°C (12°F).
• Marine Urea (AUS40) Freezing Point: Approximately 0°C (32°F).

When the solution thaws, it will return to its original concentration and be perfectly usable. Do not add any chemicals or additives to prevent freezing, as this will contaminate the fluid.

Understanding Urea Solution Shelf Life

The shelf life is directly tied to the average storage temperature. Always check the expiration date on the container and practice a "first in, first out" inventory system.

Choosing the Right Storage Container

The material of your storage container is crucial for preventing contamination.

• Approved Materials: The only recommended materials are high-density polyethylene (HDPE) and stainless steel.
• Forbidden Materials: Never use containers made of carbon steel, aluminum, copper, or brass, as they will corrode and contaminate the urea solution.
• Sealed Containers: Always keep containers tightly sealed. Urea solution can evaporate, altering its concentration, and exposure to the air can introduce airborne contaminants.

Frequently Asked Questions (FAQ)