No one is all that interested in a chemical de-icer — until they’re slipping around on the ice.
At that point, they are very important to personal and often public safety as well. The five main materials that are used as chemical de-icers — calcium chloride, sodium chloride (table salt), potassium chloride, urea, and calcium magnesium acetate — aren’t all created equal.
Calcium chloride is the traditional ice-melting product. Though it will melt ice to about 25 F, it will form slippery, slimy surfaces on concrete and other hard surfaces. Plants are not likely to be harmed unless excessive amounts are used.
Rock salt is sodium chloride and is the least expensive material available. It is effective to approximately 12 F, but can damage soils, plants and metals. Potassium chloride can also cause serious plant injury when washed or splashed on foliage. Both calcium chloride and potassium chloride can damage roots of plants.
Urea (carbonyl diamide) is a fertilizer that is sometimes used to melt ice. Though it is only about 10 percent as corrosive as sodium chloride, it can contaminate ground and surface water with nitrates. Urea is effective to about 21 F.
Calcium magnesium acetate , a newer product, is made from dolomitic limestone and acetic acid (the principal compound of vinegar). CMA works differently than the other materials in that it does not form a brine like salt but rather helps prevent snow particles from sticking to each other or the road surface. It has little effect on plant growth or concrete surfaces.
Performance decreases below 20 F.
In short, different products have different use limits and damage potential. While limited use of any of these products should cause little injury, problems can occur when they are used excessively and there is not adequate rainfall to wash or leach the material from the area. For best results, limit use by trying to remove snow and ice by hand when possible. When you absolutely must use a de-icer, use sparingly.