AUS 40 Storage & Handling
Onboard Best Practice

AUS 40 is a near-saturated solution, because 40% is close to urea's solubility limit at cool temperatures. That gives it a narrower comfort zone than automotive AdBlue:

Condition	Threshold	What Happens
Crystallisation onset	~0 °C	Urea crystals begin forming (AUS 32 tolerates −11 °C; AUS 40 does not)
Ideal storage	5–30 °C	Fluid stays homogeneous and in spec for the longest period
Elevated storage	>30–35 °C sustained	Accelerated urea hydrolysis → rising ammonia and alkalinity, shortened shelf life
Direct sunlight on packaging	Any duration	Local heating and UV exposure degrade fluid and HDPE packaging

Crystallised AUS 40 is not ruined: warm it gently above ~5–10 °C with recirculation and the crystals redissolve without changing concentration. What it must never do is sit half-crystallised in a dosing line, which is why urea tanks, transfer lines and IBC storage bays on vessels trading cold waters are heated or trace-heated. In Indian coastal conditions the practical risk runs the other way: keep drums and totes shaded and ventilated, not on a sun-baked deck.

Stored sealed within the ideal window, AUS 40 typically holds specification for 12 months or more. The clock runs faster when storage is hot: dissolved urea slowly hydrolyses to ammonia and CO₂, nudging pH and alkalinity out of the ISO 18611 / IS 17661 band.

Stock rotation rules that work

• First in, first out. Consume the oldest batch first; record batch numbers and delivery dates from each Certificate of Analysis.
• Keep containers sealed until connection to the transfer system. Evaporation concentrates the solution above 40%, and open lids invite contamination.
• Verify before dosing aged stock. If product has been aboard longer than its documented shelf life or stored hot, test refractive index / density against the CoA values before committing it to the SCR system.

Right-sizing deliveries avoids the problem entirely: order in packaging formats matched to consumption: 200 L drums for top-ups, 1000 L IBCs for coastal work, bulk tanker transfers for deep-sea rotations (consumption maths in our SCR dosing guide).

Urea solution is mildly alkaline and aggressively corrosive to the wrong metals, and every metal it dissolves travels straight to the SCR catalyst.

Compatible	NOT Compatible
Stainless steel 304/304L, 316/316L	Copper, brass, bronze
HDPE, polypropylene (PP), PVDF	Mild / carbon steel (unlined)
Fluoro-elastomer & EPDM seals	Aluminium, zinc & galvanised surfaces

Contamination control at bunkering

• Dedicated equipment only. Hoses, pumps and funnels used for AUS 40 must never touch fuel, lube oil, hydraulic fluid or seawater. See our unloading, pumping & discharge guide for hose, coupling and flow rate detail.
• Inspect before connecting. Check seals, cleanliness of couplings, and that the delivery paperwork's batch number matches the Certificate of Analysis.
• Never return drained fluid to storage, and never top up with water to "stretch" volume. Dilution below 40% under-doses the catalyst exactly like using AdBlue, as explained in our AUS 32 vs AUS 40 guide.

Quality assurance starts before the fluid reaches the ship: PROTICKS ships every batch with a Certificate of Analysis, from a plant minutes from Gujarat's major anchorages. See port-side delivery locations.