Diesel Exhaust Fluid (DEF) is an aqueous urea solution used in Selective Catalytic Reduction (SCR) systems on diesel vehicles to reduce nitrogen oxide (NOx) emissions. The solution is approximately 32.5% urea and 67.5% deionized water. Due to its water content, the solution is subject to freezing at lower temperatures. The point at which solidification occurs is approximately 12 degrees Fahrenheit (-11 degrees Celsius). When the fluid freezes, the water forms ice crystals, potentially causing expansion within the storage tank or delivery lines.
Understanding the solidification point of DEF is crucial for maintaining the operational efficiency and longevity of SCR systems. Allowing DEF to freeze and thaw repeatedly can lead to degradation of the solution and potential damage to the vehicle’s emission control components. The proper handling and storage of DEF in cold climates is essential to prevent such issues and ensure compliance with environmental regulations. Historical context demonstrates that early adopters of SCR technology experienced challenges related to DEF freezing, which prompted the development of solutions like heated tanks and lines.