It is easy to spend time choosing the right pump and nozzle, then finish the job with whatever fittings are in the shed. With AdBlue®, that can be a costly shortcut. Some very common materials react with AdBlue, corrode and release metals into the fluid. The result can be product that no longer meets ISO 22241 and problems in the SCR system further down the track.
Why materials matter so much
AdBlue is 32.5% high-purity urea in de-ionised water. The ISO 22241 specification sets very tight limits on metals. For example, copper, zinc, chromium and nickel are each limited to 0.2 mg/kg, and iron and aluminium to 0.5 mg/kg. A single brass fitting slowly corroding in the line can be enough to push those figures up.
You cannot see this kind of contamination, and a refractometer will not detect it. A refractometer checks urea concentration only. Metals and minerals can only be found with a lab test. Choosing the right materials from the start is the practical way to avoid the problem.
Materials that suit AdBlue
| Material | Typical use |
|---|---|
| Stainless steel (304 / 316) | Fittings, nozzles, pump parts, tanks, camlocks |
| HDPE (high-density polyethylene) | Tanks, IBCs, drums, containers |
| Polypropylene | Fittings, valves, camlocks, adaptors |
| PTFE | Thread tape, seals, linings |
| EPDM | Hoses, seals, O-rings |
| Fluoroelastomer (FKM) | Seals and O-rings |
Stainless steel grade 316 has slightly better corrosion resistance than 304, which is why it is often chosen for outdoor or coastal installations. Both are compatible with AdBlue.
EPDM is the most common hose material for AdBlue dispensing. It is flexible, handles outdoor conditions and is compatible with the fluid. Look for hose that is specifically rated for AdBlue or DEF by its manufacturer.
Materials to keep away from AdBlue
- Brass and copper. Very common in water and diesel fittings, and one of the most frequent causes of contamination. Watch for brass ball valves, hose tails and adaptors.
- Aluminium. Found in some pump bodies, meters, camlocks and nozzles made for diesel.
- Zinc and galvanised steel. Galvanised pipe and fittings shed zinc into AdBlue.
- Carbon (mild) steel. Rusts and adds iron to the fluid.
These parts often turn up because they are low-cost and easy to buy from a hardware store. A replacement ball valve or hose tail bought in a hurry is one of the most common ways a well-designed system ends up with the wrong metal in it. If you keep spares on site, make sure they are the right material and label them for AdBlue use only.
Also avoid any hose, fitting or container that has been used for diesel, oil, coolant or mineral-bearing water, even if it is the right material. Residue is very hard to remove completely.
Practical tips for hoses and fittings
Hoses
- Size the hose to the pump outlet and nozzle. A mismatch restricts flow or needs extra adaptors, each of which is another potential leak point.
- Keep runs as short as practical and avoid tight bends and kinks.
- Use a hose reel on fixed installations to keep the hose off the ground and away from vehicle wheels.
- Replace hose that shows cracking, hardening, bulging or crystals around the ends.
Fittings and seals
- Use PTFE tape or a compatible thread sealant on threaded joints where the manufacturer recommends it.
- Use stainless steel or plastic hose clamps. Standard zinc-plated clamps on the outside of a hose are less critical, but they will corrode and fail sooner in contact with drips.
- Check O-rings and seals are EPDM or fluoroelastomer. Generic rubber seals may swell or perish.
Spotting problems
- White crystals around a joint mean a slow leak. Clean with plenty of water and fix the seal.
- Green, blue or white corrosion on a metal part suggests it is the wrong material. Replace it.
- Discoloured fluid in a clear filter bowl or container is a warning sign. Stop and investigate.
One thing you can do today: walk the full length of your AdBlue system with a torch. Look closely at every valve, tail and adaptor. Any yellow-coloured brass, dull grey aluminium or galvanised part should be swapped for stainless steel or polypropylene.
How Liquidia can help: Liquidia supplies AdBlue-compatible Piusi hoses, fittings, nozzles and complete kits, so every part in the line suits the fluid. Browse the accessories range or read how we protect product quality on our certification page.