Choosing the Right Deicer

Choosing the Right Deicer:
Several performance characteristics should guide the selection of an ice melter, but two are particularly important:

  1.  How well does the low temperature performance of the material match the coldest temperatures you are likely to experience?
  2.  How quickly will the material melt ice to minimize pedestrian exposure to potentially dangerous conditions?

Rock Salt (Sodium Chloride, NaCl) – Rock salt is widely used, largely because it is readily available and inexpensive. However, rock salt is endothermic. It must draw heat from the surroundings to form an ice-melting brine. With a lowest effective temperature of +20°F (-7°C), rock salt is a relatively slow and ineffective ice melter when temperatures are coldest. Like all chloride-based materials, rock salt is corrosive to unprotected common metals. Lawns and other plants can be harmed if rock salt deicer is over-applied or large quantities are directly applied to grass or vegetation.

Calcium Chloride (CaCl2) – Calcium chloride is the most widely used non-sodium chloride deicer. Its lowest effective temperature, -25°F (-32°C), is below that of other common deicers. Calcium chloride is a hygroscopic material that attracts moisture from its surroundings, speeding the creation of brine to give melting action a fast start. Calcium chloride is also exothermic. As it dissolves in contact with moisture, it releases a significant amount of heat. This makes commercial products containing high levels of calcium chloride faster ice melters and more effective at colder temperatures than rock salt and other products which must draw heat from their surroundings to dissolve and form brine.

Like all chloride-based materials, calcium chloride is moderately corrosive to unprotected common metals but, in general, there is little difference in corrosion between the various chloride-based deicers, including rock salt (sodium chloride), magnesium chloride and calcium chloride. As with other chloride-based ice melters, over exposure to calcium chloride can harm lawns and other plants if deicer is over-applied or large quantities are directly applied to grass or other vegetation.

Magnesium Chloride (MgCl2) – Like calcium chloride, magnesium chloride is a hygroscopic material, able to attract moisture from the air. However, unlike calcium chloride, solid magnesium chloride is a hexahydrate salt, meaning it is 53% water by weight. Because this solid product is so dilute, more must be applied to deliver ice melting capacity equal to calcium chloride or sodium chloride. When the water content of solid magnesium chloride is factored into the measurements used to assess melting performance, the results show that it is somewhat less effective than sodium chloride (rock salt) after 20 minutes at 20°F, even though it is typically more expensive. Magnesium chloride is exothermic but does not release as much heat as calcium chloride. It has a lowest effective temperature of 0°F (-18°C).