LIQUI MOLY has introduced an AdBlue additive which is easy to use and protects the SCR system for exhaust gas treatment against damage. 

AdBlue is used to help vehicles comply with the standards for nitrogen oxide emissions that apply in Europe. However, this process can cause damage to the exhaust system and DEF Anti Crystal Additive Concentrate, newly developed by LIQUI MOLY, is formulated to combat this. 

AdBlue, also known as Diesel Exhaust Fluid (DEF), is injected into the hot exhaust tract in the appropriate doses via a separate tank. But as David Kaiser, Head of Research and Development at LIQUI MOLY explains, “The solution evaporates there. Residues can form because a liquid film forms on the exhaust pipe surface, where the water evaporates faster than the urea can decompose. The additive lowers the temperature to achieve the so-called Leidenfrost effect. This phenomenon promotes residue-free decomposition of the AdBlue solution. The Leidenfrost effect reduces the formation of a liquid film on the exhaust surface.” 

Residues can be formed because AdBlue consists of around two thirds demineralised water and about one third urea. When this substance is heated, the organic compounds biuret and triuret are formed by the separation of ammonia. “Urea crystals form in lines or in dosing valves. This happens when the water in the lines evaporates or vaporizes,” explains David. In extreme cases, this leads to a blockage in the AdBlue system. This in turn can cause damage to the pump and injection nozzles or trigger an error message in the engine control unit. To combat this, the surfactant contained in the additive reduces the surface tension in AdBlue. It hinders the formation of drops. This prevents the development of unwanted crystals and deposits on the injection nozzle. 

The additive also significantly reduces the freezing point of the AdBlue. 

LIQUI MOLY stress that the additive only has a preventive effect. Existing crystallization can only be removed mechanically. In most cases, this means expensive replacement of parts, making prevention more important. 

The new product is available in a 2.5 litre plastic container from LIQUI MOLY stockists.