When winter gets nasty, it’s very handy to have sand, gravel and anti-slip mixtures with no salt or chemicals. They reduce the risk of falling without harming grass, concrete, asphalt or paving stones.

However, spreading the product on walkways and the driveway will not get rid of the ice. Using a de-icing product can sometimes be worthwhile if it saves someone from falling head over heels and being hurt. Consumers usually rely on chloride-based de-icers. Often, that’s all they see in stores. But which is the best? Sodium chloride (salt), calcium chloride, magnesium chloride or potassium chloride?

Buyer’s guide

First, remember that price should not be the sole selection criterion for a de-icer.

The two main factors to consider are: the temperature limit at which the de-icer will continue to be effective and its corrosive potential for materials and the environment.

Sodium chloride (often called “ice-salt”):

  • Benefits: inexpensive but performs poorly below -10°C.
  • Disadvantages: Very corrosive; damages concrete and plants; needs heat (sun, etc.) to be activated; leaves white stains.

Calcium chloride:

  • Benefits: Works down to -30°C; quick-acting (generates heat by exothermic reaction); less product required than for sodium chloride; less damaging for the environment than sodium chloride when applied as directed.
  • Disadvantages: More expensive; corrosive for unpainted metal (e.g. rebar rods in concrete); can damage surfaces and plants if applied excessively.

Magnesium chloride:

  • Benefits: At least 33% less chlorine than calcium chloride; characteristics similar to calcium chloride but less efficient, only works down to -25°C; the least damaging for concrete; non-toxic for plants and animals if used as recommended;
  • Disadvantages: Corrosive for metal; may damage surfaces and plants if applied excessively.

Potassium chloride:

  • Benefits: Preferred product for plants and the least corrosive for concrete.
  • Disadvantages: Ineffective below -7°C; expensive; almost eliminated from the market because of the recent skyrocketing cost of potassium.

The crumbling of concrete and asphalt is the result of repeated freezing and thawing cycles. So it’s better to choose a de-icer that provides long-term protection against re-freezing.

The best purchase should be determined by the quantity of de-icer needed to remove ice from a given surface area. From a perspective of price/quality ratio, it can be better to pay two or three times more for a product that will de-ice four times more surface, more quickly, at much lower temperatures and with less environmental impacts.

Advice on using de-icer

Moderate use and following the manufacturer’s coverage recommendations (e.g. ½ cup per m²), are the basic rules to follow. Even products used as fertilizers, for example magnesium and potassium, can cause damage in high concentrations. To give better visual cues when spreading, some de-icers now are coloured.

For materials:

  • Apply just enough de-icer to detach the ice from the surface.
  • Remove the snow and ice as soon as the product works so as to minimize secondary effects.

Note that no de-icer should ever be used on concrete less than two years old since the material contains lime residues that can cause scaling when in contact with chloride. Similarly, it is not recommended for spreading on concrete that is non-air-entrained, cracked or scaled, or on masonry (brick, stone, etc).

For vegetation:

  • Disperse the snow and ice as you dislodge it, since heaps will produce excessive concentrations of de-icer when it thaws.
  • Grass will look better in the spring if it has had a winter protection blanket.  Designed to limit burns from de-icing salts, this kind of membrane helps to remove accumulated sand and gravel; it should be removed as soon as the snow is gone. Some are washable and reusable.
  • As soon as spring arrives, water areas that might have been affected so as to wash away any de-icer residue.

Thanks to Mr. Deshaies and Mr. Henri de Sel Warwick.