Sidewalk de-icers: effective AND safe?By Sally G. Miller (sallyg)
December 20, 2008
Are all de-icer products created equal? They sure aren't priced equally. And are they safe for people, plantings and pets? Those are burning questions in late December. In North America, winter solstice is regarded as the first official day of winter. If snow and ice haven't yet arrived in your zone, they may soon. This article will help you decide just which of the many sidewalk de-iceing products being sold is best for you.
Sodium chloride and related salts are the standard chemical de-icers.
Some of us grew up with the widespread use of salt to melt roadway ice. Some of us didn't. Salting and plowing of highways became common just in the 1960's. Salt (rock salt, sodium chloride, NaCl, halite) is the cheapest of the ice melting chemicals. It works because it dissolves in any free moisture and makes a saltwater solution, which stays liquid at a lower temperature than plain water. Rock salt is effective on roads, where friction from the traffic adds heat. Salt works well on sidewalk ice too, as long as the temperature isn't too far below the freezing point of water.
Concern over the safety and effectiveness of sodium chloride has led to the development of alternatives. Related chemical salts (calcium, magnesium, and potassium) work the same way sodium salt does. These products are often sold for the home market in handy 12 pound plastic jugs with exciting labels touting their benefits. They'll cost a little more than salt, but pound for pound they melt more ice. You'll have to examine the label to figure out just which salt is in the jug. Some of these advanced de-icers are mixtures of salts.
These four salt compounds are chemically very much alike. They react with ice, and the resulting salty solution drains away from paved surfaces. That's good for pedestrian safety but can be bad for hard surfaces, plant material in the immediate area, local natural waters and your pets. The sodium and the chloride ions are the chemical bad guys in these compounds; calcium, magnesium and potassium are considered minor or major plant nutrients. You can minimize the damage of chemical salt de-icers by using them sparingly. Let the chemical melt down through the ice layer, where it will flow and release the ice from the pavement. Use enough de-icer to make the ice easy to remove by scraping or shoveling. Scatter or spread the removed slush to dilute the salts.
Hot tips for melting ice
Sodium chloride (salt, NaCl, halite) is the cheapest de-icer. It works well in many situations.
Calcium chloride (CaCl) is the most effective chemical salt ice melter, especially at lower temperatures. It actually gives off heat as it reacts with the ice.
Use just enough de-icer to loosen and break up the ice layer.
Is it too cold for salt to work? You should see melting begin within fifteen minutes of application. If you don't, you may need another product.
Pellets or crystals work better than flakes to melt down through the ice and loosen it.
The chemical industry has responded to safety concerns by giving us several "safe" alternatives. The safer part of the formulation comes from their lack of sodium and chlorides.
Safer for pets
Pet owners can worry about chemicals in contact with their animals paws, or ingestion when a cat or dog licks its paws or eats contaminated ice. There is an ice melter on the market which isn't based on salts, but on an organic chemical, much less likely to sicken Fluffy or Fido. "Safe Paws" is one brand of this new type of de-icer, and the company has a website describing the product. (I must say that after reading other material about chemical de-icers, I would take a few of the satements on the SafePaws site with a ...yes, a grain of salt.) I was unable to find independent research comparing the effectivness of this product to a standard de-icer. Expect pet-safe de-icers to cost more than chemical salts.
Safer for plantings and environment
The sodium and the chlorides of the standard chemical de-icers can burn plant roots and foliage and accumulate in the soil. Some homeowners use lawn fertilizer, chiefly urea, to melt ice. Chemical fertilizers are equally capable of burning plants when used for de-icing. And using fertilizer to melt ice creates a nutrient rich runoff that contaminates natural waters. Do not use inorganic fertilizers to melt ice.
Calcium magnesium acetate (CMA) is another new de-icer that may be of interest when environmental and landscape safety is a priority. CMA contains the relatively safe calcium and magnesium you read about above, and is produced by a reaction of limestone and acetic acid (vinegar). CMA is sold for homeowners in the handy jug. CMA's low temperature effectiveness ranks with that of magnesium chloride; however, CMA tends to leave a grainy slush on paved surfaces that may not be sufficiently safe for some homeowners. Wisely limiting your use of chemical salts may be adequate in avoiding salt burn in your yard.
Safer for surfaces
Salt de-icers can cause damage to pavement and metals. Concrete damage by the salts stems not directly from the chemical itself, but from the freeze-thaw cycles that occur in combination with de-icer use and winter weather. In testing cited in "The Effect of Common Deicers Upon Concrete", (linked at right), calcium chloride was judged the least corrosive of chemical de-icers. Urea (nitrogen fertilizer) was the most agressive tested substance in terms of concrete attack, with ammonium being directly corrosive. (That's another good reason not to use chemical fertilizer as a de-icer.) Good, sound concrete and painted metals should resist damage from properly used de-icers. Use a light layer of chemical and manually remove the slush and ice once it's loosened from hard surfaces to minimize property damage.
Chemical names in shorthand
Sodium chloride = NaCl
Calcium chloride = CaCl
Magnesium chloride = MgCl
Potassium chloride = KCl
Calcium magnesium acetate = CMA
Great links for further reading:
Safe Paws FAQ page
American Veterinary Medicine Association article "Winter Pet Care Tips
Read all about Winter solstice in Wikipedia
All pictures taken by and property of the author.
Safety of your family and friends is foremost. You can use de-icers to help assure their safety, as well as the safety of pets, property and environment.
Sidewalk de-icers CAN be both safe and effective. Choose the product most suited to your situation. Use just enough to break up and loosen the ice for physical removal.