De-Icer Quantification and Phase Transition Detection by Raman Spectroscopy 2013-01-2101

Winter maintenance is based on the intervention of operating services, as well as the use of deicers. Each year, in France, thousands of tons of deicers are spread through runways and taxiways. On the airport sector, the main deicers are sodium or potassium acetates and formates. All these deicers aim to prevent ice formation (preventive strategy) and/or improve the ice melting of snow residual film (curative strategy) at temperatures below 0°C. The operating principle of these compounds is based on the lowering of the solution's freezing point once dissolved in water. The phase diagram's knowledge is predominant to determine the deicer's amount to be applied on the surface. It provides a way to optimize their amounts applied with respect to weather conditions, present or forecasted.

The Center for Technical Studies of Equipment in East of France (CETE de l'Est) developed and implemented a method based on Raman spectroscopy to characterize aqueous solutions of airport de-icers. This application determines the phase transition temperatures of these solutions, according to their concentration. The spectroscopic tool being portable, its use could be easily conducted on the field, avoiding any sample collections. Furthermore, this spectroscopic tool enables the determination of the amount of de-icers used to generate the solution. This study also highlighted some differences between the freezing curves of different deicers, as well as the possible presence of phases with unknown chemical and mechanical properties, such as the metastable phase potassium formate. Additional lessons related to winter maintenance could be taken, on the shelf-life of these products as an example.