Technical Bulletins > CF7
03/23/08 - Proper Use of Cryotech CF7 and NAAC
Instructions on how to properly use deicing chemicals when dealing with snow, freezing rain, and ice.
Liquid CF7® (potassium acetate) is generally used as an anti-icer to prevent snow and ice from bonding to the surface. The snow and ice can then be easily removed by broom or plow. Solid NAAC® (sodium acetate) is used as a deicer. It is also applied early in the storm but its purpose is to melt through an existing pack and break ice-to-pavement bonds prior to mechanical removal.
CF7 is more efficient than a solid deicer when applied as an anti-icer because it takes less energy to prevent surface bonding than to break existing bonds. Therefore, early liquid application followed by mechanical removal of snow and ice accumulation provides the best and most efficient method for combating winter storms.
"Early application" means applying just before the event or as precipitation begins to fall. Reconmended CF7 rates range from 0.5-1.5 gallons per thousand square feet (25-75 grams per square meter) depending on weather conditions. It is also important to evenly apply the fluid using low-pressure, large droplet nozzles. Surfaces can then be cleaned mechanically until bonds reform and dilution requires additional applications.
How long will it last? Water from snow or ice melt will dilute the CF7, thereby raising the solution freeze point. Depending upon conditions such as air and surface temperature, type and amount of precipitation, and deicer application rate, at some point the dilute solution will become ineffective and re-application will be necessary. The clearest signs that dilution has occurred are low friction and unsatisfactory snow or ice patches remaining after mechanical removal. Dilution can also be determined by computer monitored roadway sensors.
Solid NAAC is generally applied as a deicer on top of the snow or ice pack, but always early in the storm whenever possible. Pack results from surface bonding of snow and ice and is difficult to remove with liquid deicers. It is common for pack to build on roadways as well as on secondary areas like ramps that may not receive anti-icing treatments.
NAAC is applied on the wet area, ice, or pack. As it combines with moisture, NAAC changes from a solid to a liquid. This exothermic phase change – unique to NAAC – releases heat allowing each pellet to quickly penetrate the pack and break surface bonds. Application rates range from 5-15 pounds per thousand square feet (25-75 grams per square meter). Again, it is important to achieve even application. Because NAAC is produced as spherical pellets it spreads more evenly than flaked products.
In certain conditions, CF7 may be used with NAAC to assist with breaking up a heavy pack. After holes are formed by NAAC, CF7 is applied over the top and thereby has a direct route to the pavement surface. This dual application speeds the deicing process.
CF7 is also recommended as a prewetting agent for NAAC to jump-start its phase change. This prewet also causes the solid to stick to the surface, minimizing product loss from wind or vehicle movements. During freezing rain, NAAC may be helpful when applied with CF7. This dual application extends operations by minimizing dilution of the liquid.
NAAC and CF7 should not be combined during routine anti-icing operations. CF7 is more efficient and the addition of NAAC is generally not helpful. The exception is use in the aforementioned freezing rain condition.
Technical assistance and on-site training are available by calling Cryotech at 800-346-7237.
